Abstract: Shale gas has various forms of occurrence, mainly in the free and adsorbed state, and the main controlling factors of shale gas in different occurrence states are quite different. Comprehensive evaluation of shale gas systems has not yet been documented. Therefore, the actual data of production characteristics of Fuling national shale gas demonstration area in the east of Sichuan Basin were studied by means of geochemical analysis, petrophysical testing, isothermal adsorption experiments and on-site desorption of shale in the Wufeng-Longmaxi formations. The main controlling factors of shale gas content in different occurrence states were identified as the following. The evaluation of shale gas content mainly includes the evaluation indexes of six categories and six parameters:direct index (measured gas content, gas detection value and gas saturation) and indirect indicators (porosity, resistivity and formation pressure) for gas qualitative and semi-quantitative evaluation system.