Based on the organic geochemistry and reservoir analysis experiments of drilling core samples, the shale gas accumulation conditions of the Cambrian Niutitang Formation and the Silurian Longmaxi Formation in Northwest Guizhou are compared. The original TOC of shale of Niutitang Formation and Longmaxi Formation is 8.68,~10.50, and 0.60,~9.45, respectively, the original hydrocarbon generation potential is 62.77~75.20 mg / g and 4.44~69.70 mg / g respectively, and the average gas production is 93.35 cm3 /g and 58.58 cm3 /g respectively, which proves that the original hydrocarbon generation capacity of Niutitang Formation is much better than that of Longmaxi Formation. The maximum adsorbed gas content of shale of Niutitang Formation and Longmaxi Formation is 1.81~9.07 m3 / t and 2.24~2.49 m3 / t respectively. The pore size is mainly distributed in the range of 3.48~3.65 nm. The total pore volume and specific surface area of Niutitang shale are generally smaller than those of Longmaxi shale. Comprehensive study shows that Niutitang shale is more conducive to enriching adsorbed natural gas than Longmaxi Formation shale. However, shale gas of Niutitang Formation is formed much early and evolved for a very long time, which leads to the loss of most natural gas, the decrease of shale porosity, and the decrease of free gas enrichment capacity. Thus, the gas accumulation capacity of Niutitang shale is weaker than Longmaxi shale.