The wind turbine blade is a key component of wind turbine generator system, and helps capture wind energy effectively. The way of RTM resin transfer molding is generally used at home and abroad for blade manufacturing process. In order to ensure the quality of product, computer simulation analysis and experimental verification should be conducted before producing. Moldflow was used to simulate the process of wind turbine blade RTM. Based on that, variation diagrams about filling time, temperature, buckling deformation, pressure and so on are obtained. The results of analysis and comparison of with and without cooling, as well as optimize the defects existed indicate that cavitations concentrate in roots and edge of the blade, gas exhaust mold easily, there is no need to open up air vent additional; In filling stage, mold clamping force gradually increase slowly, in packing stage, mold clamping force sharply increase to reach peak, the mold clamping force disappears after packing; filling time with cooling process is longer than that without cooling process. It provides an important reference for wind turbine blade design and manufacture.