 He claimed that his great-grandfather Dong Wenyu () was a prefectural prefect; his grandfather Dong Xuanjiang () was an officer under the Protectorate General to Pacify the East; and his father Dong Shenjiao () served as a military recruiting officer.Dong Qin became a soldier when he was young and was said to be unusually capable and strong.He successively served three military governors ("Jiedushi") stationed at You Prefecture — Xue Chuyu (), Zhang Shougui (), and An Lushan, and because of his accomplishments received repeated promotions, eventually receiving a title as general and forward commander at one of the circuits that An governed, Pinglu Circuit (平盧, headquartered in modern Chaoyang, Liaoning).