The widely used of hydraulic fracturing in unconventional gas reservoirs with ultra-low permeability has greatly increased the gas production. While there are two main problems associated with water-based fracturing fluid in shale reservoirs, formation damage and long cleanup time, which pose a threat to the shale gas production. In order to eliminate the disadvantages induced by viscous water-based fracturing fluid, liquid CO2 with very small viscosity has been successfully applied as a kind of fracturing fluid. As an inert gas, CO2 has little interaction with gas shale, so it effectively avoids the formation damage; and the gratification CO2 in reservoirs returns to the surface with a short cleanup time. The main aim is to investigate the performance of CO2 as a fracturing fluid in shale reservoirs and to compare the difference between water-based fluid and fluid CO2 in the fracturing effectiveness.