Traditional shale gas productivity models do not consider the effect of gas-water two-phase flow on the productivity during the backflow of fracturing fluid. This study proposes a new shale gas productivity model that considers the effect of gas-water two-phase flow as well as the effect of shale gas adsorption，desorption，diffusion，slippage，stress sensitivity，and capillary imbibition. The model calculates the productivity of shale gas and the distribution of formation fluid saturation using the SS method based on the finite difference theory. The model was applied to a real field case to analyze how shale gas productivity was affected by the permeability of fracture network，the permeability of artificial major fractures，the length of artificial major fractures，the adsorption and desorption of shale gas，and the capillary force on shale gas. The results were compared to field observations. In the early period of production，the daily shale gas production first raised，peaked，and then dropped due to the backflow of the fracturing fluid. Compared to the case considering no backflow of fracturing fluid，the case considering the backflow of fracturing fluid has significantly lower shale gas production at the early period but similar production at the later period. The shale gas production at the early period increased with increasing fracture network permeability，artificial major fracture permeability，and artificial major fracture length. The shale gas adsorption and desorption had little effect on the shale gas production at the early period. The capillary force，however，would lower the backflow rate of the fracturing fluid，thus increasing the shale gas production，which is consistent with field observations.