The X- ray diffraction technique was used to qualitatively and quantitatively analyze the core samples of the 2nd Member of the Kongdian Formation of the well Changyecan- 1 in the Weibei sag. The results show that the mineral composition of the 2nd Member of the Kongdian Formation is mainly composed of clay minerals, quartz and calcite, with an average content of 51. 7%, 29. 3% and 9. 6%, respectively. In addition, there contains feldspar and a small amount of dolomite, and pyrite, et al. The mineral composition reflects that the deep lake- semi- deep lacustrine sedimentary environment in the second part of the Kongdian Formation, providing a certain sedimentary condition for the formation and storage of shale gas reservoirs. The clay mineral composition reflects TOC of the Kongdian store evolved into a mature- high maturity stage with maturity conditions for shale gas formation. In short, the mineral composition has certain positive significance for the formation and development of shale gas reservoirs. The thickness of the two layers of shale gas in the second Member of Kongdian Formation is 60. 48 m and 68. 09 m, respectively. The illite and chlorite content is low and the corresponding pores are the high rate and granular mineral (quartz+calcite) content is between 30% and 50%, which is an ideal shale gas key exploration and development horizon.