Although multi-stage fracturing of horizontal wells has been used as the main method to develop shale gas, a long time for fluid recovery and the small amount of fluid recovered with only 10% to 50% of total pumped have led to concerns that phase trapping of fracture fluids may do serious damage to gas reservoir. The experiments of fracturing fluid leakoff and spontaneous imbibitions have been investigated with Longmaxi shale in the eastern Sichuan Basin, and the process of water flowback was surveyed, and then evaluated the impact of rising water saturation on gas-transport and propagation ability of pressure. Experiments results reveal that water saturation in shale is more than 40% after fracturing, but water amount and rising rate are much higher in fractured shale. Much of the load water that is not recovered from pores is effectively blocking gas flow path, and decreased permeability, diffusivity and propagation speed of pressure, and then form water phase trapping. It is concluded that water phase trapping damage is mainly caused by nanopores, abundant hydrophilic clay, and ultra-low water saturation. Furthermore, the load water has led to more gas-transport resistance,and decreased the supply capacity of gas flowing from matrix to fractures. Therefore, it is a promising and significant work to investigate the fluid flow-back mechanism, optimization of surfactant, and the application of non-aqueous fracturing technologies and heat treatment for alleviating or eliminating water phase trapping damage in shale gas reservoirs.