Among all failure modes of high-power electromagnetic relays,the one caused by splashing of welding take a relatively high portion. The splashing may cause short circuit and electrical breakdown between contactor. In actual situation,the yoke iron assembly tend to lack of spot welding strength and severely splash metal remains. To solve this problem, simulation of the yoke iron assembly spot welding process is used in this work. Welding structure improvement and processing parameter optimization are used to solve problem of splashing. In general,the reliability and stability of high-power electromagnetic relays are enhanced.