Abstract: Yanqi basin is one of the small coal-bearing basins of Mesozoic and Cenozoic in W est China. Since 1993, two oil-gas fields with fouroil-bearing blocks have been found successively. The Jurassic source rocks in coal measure strata are mainly distributed in Bohu depression,forming Jurassic petroleum system. Through quantitative statistics of petroleum micro-constituents from wells by sample analysis and study ofvarious coal-measure facies parameters in Yanqi basin, it is found that they are high in gelation index and low in plant tissues restoring index,proving that most coal measures are formed reducing environment with weak water mobility. The coal measure facies can be divided into fiveones such as dry peat marsh, moist forest peat marsh, transitional margin marsh, living water peat marsh and open water facies. It is pointed out .that the coal-bearing formation in transgressing sequences is favorable environment for hydrocarbon generation in Jurassic coal measure sourcerocks in Yanqi basin.

Key words: Xinjiang, Y anqi basin, Jurassic, source rock, organic facies