Abstract: The best source rocks, is a prerequisite for further oil and gas exploration in the sedimentary basin, hydrocarbon source rock evaluation of oil and gas migration, accumulation, basic research. The Permian reservoir in the Northwest Sichuan Basin has two sets of source rocks, source rocks for the two Permian Qixia and Maokou group, the other is a two Permian hydrocarbon source rocks in Dalong formation，compared with the two Permian source rocks, with its geochemical characteristics and geological significance of hydrocarbon formation in source rocks. For this reason, the type from the source rocks of Dalong formation matter abundance, starting with the maturity, chemical parameters of the earth, to conduct a comprehensive evaluation. In the northwest of Sichuan two Permian Dalong formation source rocks, the average organic matter content rich, high abundance of organic matter (average 5.68% TOC), good organic type (I - II1), a high degree of thermal evolution, and source rock is mature. (average Ro 0.87%), and the comprehensive evaluation of the hydrocarbon source rocks is a good source rock.