Abstract: The Western Sag of Liaohe Basin, which keeps the longest time of lake sedimentation in the basin, is an ideal area for the research of shale gas accumulation conditions of Shahejie Formation in Liaohe Basin. On the basis of data collection, processing and analysis, it is concluded that, the dark mudstone in the study area is mainly developed in half deep-deep lake environment with thick bottom, good continuity and wide distribution. The abundance of organic matter in mudstone is high, with average TOC around 2.18%. The kerogen is dominated by type II, preferring to produce gas. The maturity of organic matter is generally greater than 0.59%, suggesting that the shale has entered the major stage of hydrocarbon expulsion. The contents of brittle minerals are up to 43.1%-61.5%, which is advantageous for the exploitation of shale gas. Comprehensive analysis of the geological factors of shale gas accumulation shows that the Qingshui subsag serves as the favorable area for shale gas exploration in the Western Sag.