IGCT is a kind of new type power electronic device which developed from GTO and IGBT . In this paper, Author based on analysis of the internal structure of GTO, shows how GTO development IGCT through technical methods.Through simulation of its off and on performance, the work curve and comparing results of the two devices are given. Then on two components of the inverter circuits are analyzed and compared. Thinking in large power AC drive locomotive, IGCT inverter is greatly simplifier than GTO inverter circuit, and superior performance,it will become the main converter for AC driving locomotive.