Based on a comparative study of the hydrocarbon source rocks evaluation indexes of organic matter abundance, type and maturity between samples from four shallow drill holes and outcrop samples of Permian Maihanhada Formation, Aqide Formation and Haersuhai Formation, and between core samples of XT9 well and outcrop samples of Ganquan Formation of Dahulishan section, the authors hold that the influence range of intense weathering on the source rocks evaluation indexes of organic matter abundance and normal type(H/C-O/C) is over 50 m, and the extents of influence on various evaluation indexes are somewhat different. On such a basis, organic matter types of outcrop samples can be effectively divided.The influence range of intense weathering on the vitrinite reflectance (R_o) is less than 10 m.oft-com:office:office" />