A faded yellow teddy bear that passed through Ellis Island in 1920 will soon return to the main immigration building, to be displayed against the side of an open battered suitcase. The suitcase contains a German Bible with a four-leaf clover pressed inside.

Nearby, a collection of antiquated passports from dozens of countries will be displayed. In another room will sit a simple wooden 10-piece puzzle of a steamship used by the chief medical examiner of the island until 1916 to test the mental fitness of scores of new arrivals.

While workers toil to complete $140 million in renovations at the main building, its expected contents were announced this week by officials of the Statue of Liberty-Ellis Island Foundation Inc., which has raised $308 million for the statue and Ellis Island.The organizers said the immigration building would be a museum of artifacts and oral recollections commemorating the nation's heritage. Photographs and Tapes

''This exhibit is about the movement of people around the world,'' the president and chief operating officer of the foundation, Stephen A. Briganti, said. ''It is about why they went, where they went, and what they did when they got there.''

Providing 100,000 square feet of exhibition space, the turn-of-the-century building has more room for pictures and remnants than any other museum on immigration to the United States, the foundation said. The collection will include photographs by Lewis Hine, a library for scholars and a room of tapes of alumni of the island. There will also be a wall with the names of thousands who passed through the building and had donations of $100 or more made in their honor to help the reconstruction.

With plaster falling in hallways and boards covering the tiled floors, construction workers are two years away from completing the renovated building, which opened in 1892, a year after Congress had stripped the states of jurisdiction over immigration and put it under Federal control. Much of the original structure was destroyed in 1897 after a serious fire. The main building reopened in 1900. Although a ferry route has not been decided, the organizers said they were considering a site near South Ferry and were also contemplating ferries between Ellis and Liberty Islands. On the Fourth of July

The one and a half million visitors expected to visit the museum each year will begin their visit at the same dock where most of the immigrants between 1892 and 1954 landed.

''Finally we arrived in New York Harbor,'' recounts an unidentified man with a slight accent, one of hundreds who have been taped for replay in the museum. ''It happened to be on the Fourth of July, 1905. Of course, I read a lot when I was in Russia about America. And when I heard the shooting, I imagined that the Indians are shooting. I heard the Fourth of July celebration shootings.''

A woman with a frail voice said: ''People were crying. They were hysterical. They were told they have to go back. Some people had trachoma. Some people, they found lice in their hair. They were terrified at that time to get off the boat.''

As with their ancestors, visitors will arrive under a rebuilt canopy in front of the awe-inspiring south facade of the main building, with its pair of limestone eagles clutching shields of the Stars and Stripes. The visitors will enter through a glass-enclosed foyer that leads to the baggage room. The immigrants began their average five-hour stays on the 27 1/2-acre island by collecting their belongings after what was often an arduous passage in steerage. Houston St. or Texas? The baggage room, a reception area, is being restored to include a smattering of trunks and suitcases and the most common possession of an earlier time, feather mattresses. Directly behind the baggage room, the ticket office was often the last place newcomers passed through before leaving the island.

''Most people did not speak the language,'' Mr. Briganti said. ''So they might want to go to Houston Street. They would ask for a ticket to Houston, and they would wind up in Texas.''

In place of the ticket office, ''The Peopling of America'' exhibition will have a panorama of displays of 400 years of immigration, including charts, maps and graphs on the history of movement to the United States.

A rebuilt staircase leads to three exhibitions on the second floor. It was the original staircase that presented the first test for many of the 17 million arrivals who came to the new land through the island. Inspected by doctors and officials as they walked, immigrants would be marked an ''L'' by chalk if they limped, an ''H'' if they showed signs of heart trouble or an ''E'' if eye problems were detected. 'It Was an Ordeal'

''Ellis Island was considered by everybody, all the immigrants, as a purgatory, something you had to go through,'' an unidentified man said on a tape. ''It was an ordeal.''

At the top of the staircase is the registry room, a 180-foot-long great hall used as a processing center. Overhead soars a 58-foot barrel-vaulted ceiling built in 1918 with 28,258 tiles by the Guastavino Brothers, the same contractors who constructed the ceiling of what is now the Oyster Bar at Grand Central Terminal.

The registry room, restored to look as it appeared between 1918 and 1924, will be left barren of exhibitions, ''a room for contemplation,'' a foundation spokeswoman, Beverly Siegel, said.

To the west will be the American Immigrant Wall of Honor. In an effort to help raise the remaining $14 million to complete the restoration, the foundation is selling wall listings for $100 each. The wall has room for 100,000 names. About 1,000 listings have been sold. Tribute to Workers

The foundation also is trying to raise money by direct mailings and requests to corporations and other foundations. The organization's address is 52 Vanderbilt Avenue, New York, N.Y. 10017-3808.

Fourteen rooms encircle the immigrant wall and make up an exhibition called ''Ellis Island Processing.'' It will pay homage to the thousands of doctors, nurses, Government officials and other workers on the island. One young interpreter, Fiorello H. La Guardia, became the 99th Mayor of New York.

''It will really be the story of one group of immigrants processed by what was often the previous group of immigrants,'' Mr. Briganti said.

The exhibitions will focus on the legal and medical treatment by immigration officials and will describe the conditions surrounding the 2 percent who were turned back to their homelands.

Off to the eastern side of the registry room, 10 smaller chambers will house an exhibition detailing the peak immigration years of 1892 to 1924, before immigration laws sharply curtailed the flow. The exhibition will describe the conditions leading to the exodus from abroad, the movement from small towns to port cities and the odyssey across the ocean.

Photos of Ellis Island buildings under construction and items to be displayed in museum (NYT/Angel Franco) (Pp. 1 and 4)