The Longtan Formation in the Dafang area of Northwest Guizhou is characterized by alternated shale, coal seams, and sandstones, with typical characteristics of marine-terrestrial transitional facies. On the basis of profile measurement and sample collection, combined with XRD analysis of whole rock and clay minerals, determination of total organic carbon (TOC) measurement, rock pyrolysis, kerogen macerals, and vitrinite reflectance (R_O) analysis, the development characteristics of hydrocarbon source rocks of the Longtan Formation in the study area are studied and evaluated. The results indicate that: ① The minerals in the rocks of the Longtan Formation are mainly clay minerals with strong adsorption capacity, but there is a significant negative correlation between clay mineral content and quartz content (R>0.8), especially the clay content of over 70% in shale and the lower brittleness index, which is very unfavorable for fracturing development; ② The abundance of organic matter in the Longtan Formation is significantly controlled by lithology. The coal seam has the highest TOC content (average 42.9%) and hydrocarbon generation potential (average 2.68 mg/g), indicating strong hydrocarbon generation potential of coalbed methane; The hydrocarbon generation potential of shale is less than 2 mg/g, but about 80% of the samples have TOC content exceeding 2%, and the shale gas resource potential is less than that of coalbed methane; Silty sandstone has the worst hydrocarbon generation potential, with an average hydrocarbon generation potential of 0.13 mg/g and a TOC content of 1.4%~5.6%, indicating a certain degree of tight gas potential; ③ The macerals of the Longtan Formation kerogen are mainly composed of liptinite and vitrinite, with type Ⅲ kerogen being the main type and type Ⅱ₂ being the auxiliary type. They have a high degree of thermal evolution and are in the stage of high-over mature dry-gas generation; ④ The middle section of the Longtan Formation, where coal seams are more developed, is a favorable zone for joint exploration of coalbed methane, shale gas, and tight sandstone gas in the Dafang area.