From the perspective of promoting safe production and workers protection,introduce the device of electric welding machine and circuit system and protect the welding operator,which mainly includes the residual current operated protection device,electric welder no-load automatic protection device. The main function of these appliances is to play the role of security protection for electric welding machine and related equipment and operating personnel. The scope of protection is mainly electric welding machine overload;short-circuit electric welding machine and its line;casing and the welding circuit leakage;electric welding machine and line in direct contact with the electric shock and the casing and the welding circuit leakage caused by indirect contact electric shock;secondary noload voltage electric shock.