Oil shale is an important potential strategic resource to guarantee China’s energy security, and in-situ conversion is the necessary way for industrialized development of oil shale. Under the action of high temperature, the organic matter in oil shale is cracked in-situ to generate hydrocarbons, while the decomposition of inorganic minerals will change the pore permeability structure of oil shale, which will have an impact on the heating efficiency of in-situ conversion and oil and gas production. A numerical calculation model considering the decomposition of inorganic minerals in-situ conversion was developed and analyzed as an example of oil shale in Songliao Basin. The results show that the release of pores by calcium carbonate pyrolysis can improve the pore structure and enhance permeability, which is favorable for oil and gas transport. The higher the calcium carbonate content under the same mining time, the larger the porosity and permeability, and when the calcium carbonate concentration is 6%, the energy return of in-situ conversion reaches up to 9.5. The increase of calcium carbonate concentration is favorable to reduce the heating mining time and improve the heating efficiency, and the carbon dioxide produced by the decomposition of calcium carbonate with high concentration inhibits the oil and gas generation, and the thesis has a guiding significance for the preferential selection of the dessert area of the in-situ exploitation of the oil shale.