Abstract: This paper presents a new method to optimize inverter-type Welders by using an assisting circuit. Such effects can be achieved as reducing the capacity of main transformer and the current rating of switching elements. The surging current during igniting arc by short-circuit is also decreased. The main circuit can be turned off automatically at empty load and thus the efficiency is enhanced. The work mechanism for the method is discussed in detail in this paper and the conclusion is proved by experiment results.