Abstract: This paper analyzes theoretically the mechanism of magnetic switch for excimer laser,in detail,and points out that the main factors of effecting of operating characteristics of multistage LC magnetic switch are the match of saturation inductance and unsaturation inductance of stages,properly selecting of capacitors and section area of magnetic switch.Corresponding to this analySis,the principles ofdesigning of magnetic switch are concluded.A new magnetic switch is developed,which has high output power over 1kW,effectiveness 88.6%,pulse width 80us.