Inverter welding machine overcomes the defects of low power density, poor control performance and low energy efficiency of traditional welding machine, which is an important milestone in the development of electric welding machine. In recent years, inverter welding machine has achieved great breakthrough in power platform, control system and process realization, and has become the mainstream product. This paper first briefly describes the basic situation of two critical technologies of inverter welding machine: the main circuit power conversion technology and power control technology; then discusses the development of inverter welding machine in the aspects of ultra-high inverter frequency, full digital control system and green welding process. Simple, sensitive, accurate, intelligent, green and efficient will become the future mainstream development direction of inverter welding machine.