To discover the effect of fracturing parameters on gas production in horizontal wells of shale gas reservoirs, numerical simulation of staged cluster fracturing and gas flow has been carried out. The model of fracture propagation has taken the effect of stress shadowing into account. The model solved stress and displacement discontinuity with displacement discontinuity method, coupled fluid flow in the wellbore and fractures and has been solved by Newton iteration method. Taking viscous flow, Knudsen diffusion and adsorption-desorption, shale gas flow after fracturing has been solved by using discrete fracture model. Simulation results show: As to simultaneous propagation of multiple cluster fractures, when fractures spacing become smaller, the deviation angles of side fractures from maximum horizontal principle stress direction become larger, and the width of middle fracture becomes smaller. When fracturing stage number of horizontal well increases, cumulative gas production increases with a decreasing rate. As to a fracturing stage, cumulative gas production of three clusters is larger than that of two clusters. The larger fractures spacing is, the larger cumulative gas production is.