Abstract: In the exceptional inter-salt non-sandstone reservoirs in the Qianjiang Depression of the Jianghan Basin, source rock is also reservoir rock. In the sequence, the source rock's quality is good, the HC generation ratio is high, and the seal is completed, too; but the reservoir bed's permeability is very low, so the conditions of oil migration are poor. Inter salt crude oil in each reservoir is independent in non fractured areas, but many evidences of oil maturity and biomarks all show that inter-salt crude oil generally has mixture source characteristics. The crude oil in place has always been mixed with mature oil migrated from other areas. This implies that mature crude oil can migrate from generation depressions to high structural areas through low permeability reservoir beds. The homogeneity of inter-salt crude oil obviously reveals that inter-salt crude oil is derived from bacteria and algae in high salinity, high sulfureous and strong reduction environment.