Based on field profiles and data of drilled wells in Ili Basin, the analysis has shown that the thick Carboniferous lithosomic body was overlapped on pre-Carboniferous metamorphic basement rock. It can be divided into five formations, C1d, C1a, C2y, C2d and C2k, in which C1a and C2d Formations are source rock. Two kinds of Carboniferous source rocks, argillaceous rock and dominant carbonate rock, are common inC1a and C2d. The relatively high abundance of organic carbon and theⅡ2 toⅢ types of kerogen reveal it belongs to good source rock. Thermal evolution of organic matter is up to high maturity to overmaturity. Three source-reservoir-cap assemblages can be distinguished. Comprehensive analysis indicates that the Carboniferous rock is well potential for oil exploration and theC1a Formation is the target, especially the Southern Depression is a favorable area.