Abstract: In recent years, a lot of hydrocarbons have been discovered in the Carboniferous igneous rocks of Ludong area in Junggar basin, which shows great hydrocarbon exploration potentials. However, the proved or discovered commercial oil?gas flow is distributed in the weathering crust reservoir in the top of the Carboniferous, only hydrocarbon shows are found in the inner reservoirs without oil?gas flow. The comparative analysis of the characteristics of weathering crust and inner reservoirs as well as hydrocarbon exploration potential shows that the porosity of the igneous reservoir appears two peaks with increasing distance from the Carboniferous top unconformity surface, which are corresponding to two secondary karst zones. The first one means the weathering crust reservoir, the second one means the inner reservoir; It is found that the amount of gas resource is about 1 750×108 m3 in the inner reservoir, and the slope zone will be the favorable gas exploration area for the inner reservoir of Carboniferous igneous rocks in Ludong area