Abstract: Based on the thermal physical properties of a new type of erosion-corrosion resistant copper alloy (ZCuAl7-7-4-2) and the geometric and structural characteristics of three-way valve, the casting process of three-way valve is numerically simulated. The bottom and bottom-rain gating systems are designed, and their casting qualities analyzed. The numerical simulation results show that the casting quality obtained by bottom-rain gating system is better and that the casting quality is even better when the inner runner concentrates in the middle thin-wall area. The optimization combination of pouring temperature, filling speed and preheating temperature is explored by the orthogonal test. The optimal casting process is that the gating system should be the one with the inner runner concentrated in the middle thin-wall area of the bottom-rain gating system, with the pouring temperature of 1 100 ℃, the filling speed of 4.5 kg/s, and the preheating temperature of 150 ℃.