The disadvantages of air-conditioner’s triple valve in HPb59-1 alloy processed by traditional solid state hot forging, such as larger forming loads, lower material utilization, larger subsequent machining allowance, nonuniform microstructure, are put forward. However, semisolid diecasting forming which can overcome the above shortcomings is a fascinating technology. The process paremeters which had a larger influence on filling ability of semisolid slurry and casting quality, such as pouring temperature, shot velocity and preheated temperature of the die, were chosen. Furthermore, based on orthogonal test, the semisolid diecasting process of a certain type triple valve was simulated with FLOW-3D. According to the analysis of temperature field, pressure field and surface defect concentration, the optimal process parameters such as pouring temperature 897.25 °C, shot velocity 1.5 m/s and preheated temperature of the die 260 °C, were obtained, and the effectiveness of the technology was well demonstrated by numerical simulation.