Substantial coal measure gas is reserved in the Upper Permian shale in western Guizhou, China, but the mechanism of gas generation and enrichment remains unclear. In this study, rock-eval pyrolysis, stable carbon isotope, and low-temperature N2/CO2adsorption (LN2/CO2A) experiments were conducted on coal measure shale collected from western Guizhou. The geochemical composition and pore morphology were clarified, and the shale gas generation and storage characteristics were ultimately revealed. The results show that the total organic carbon (TOC) contents of most samples exceed 2%, indicating a high organic matter (OM) abundance. The average Roand Tmaxare 2.89% and 576 °C, respectively, corresponding to the overmature stage, leading to the poor current hydrocarbon generation potential. Unlike marine shale with dense organic pores, these pores are generally poorly developed and heterogeneous in the samples. Densely distributed microfractures are favorable methane migration channels. The pores are dominated by mesopores, with an average pore volume (PV) proportion of 53.55%, while the specific surface area (SSA) is mainly contributed by micropores. The LCO2A-SSA and LCO2A-PV show a positive correlation with the TOC, Tmax, and S1, but the LN2A-SSA and LN2A-PV are poorly correlated with these parameters, indicating that micropores are mainly derived from organic pores and that hydrocarbons generated by OM pyrolysis are mainly reserved in micropores. When δ13COMshows a negative anomaly, Ro, Tmax, and S1all show a negative drift in the vertical sequence, suggesting that the chemical parameters are closely related during thermal maturation. Accompanied by hydrocarbon generation, 12CH4is preferentially separated from the OM, resulting in a higher δ13COM. Meanwhile, the generated methane is mainly reserved in the form of adsorption, and the micropores/mesopores provide a favorable place for shale gas storage.