 Nothing is known about Xu Yuanlang's background other than that he was from Yan Province (兗州, roughly modern Jining, Shandong).He rose against Sui Dynasty rule in or before spring 617, and after he captured Dongping (東平, in modern Heze, Shandong), he expanded his territory, stretching from Dongping to Langye (琅邪, in modern Linyi, Shandong), and had more than 20,000 men.In spring 618, after another major rebel leader, Li Mi the Duke of Wei, achieved a great victory over the Sui general Wang Shichong and approached the Sui eastern capital Luoyang, Xu Yuanlang, along with several other key rebel leaders, nominally submitted to him and requested that he take imperial title, but Li declined.