In the period of Feixianguan, the northwest of Sichuan was a platform which was controlled by Longmen mountain island chain.Deposited in here was a set of grain carbonate and purplish red shale.Poor at the contend of organic carbon,it is impossible to be available for source rock.Based on the comprehensive study of gas chromatographic,carbon isotope and biomarker of the residual oil,it is believed that the oil is the product which was generate by argillaceous source rock of Cambrain.in oil-generation peak.