Abstract: Qijiazi sag is an oil sag in the north of Zhangqiang depression, the main oil-bearing beds are from Xiasha formation, which can be divided into Ⅰ and Ⅱ oil groups, both belonging to self-generating and self-preserving type. The hydrocarbon source rocks of the Qijiazi sag are mainly of dark mudstone, with a large thickness, pure mass and wide distribution area. Organic type is mainly of humic substances to sapropel type and sapropel to humic substances type. Based on the analysis of hydrocarbon source rocks of organic carbon, chloroform bitumen ‘A', total hydrocarbon, potential hydrocarbon generation and hydrocarbon conversion rate, hydrocarbon source rocks have high abundance of organic matter and belong to good oil source rock, which provides adequate oil for all kinds of traps in the south area.