Nowadays the steel rails gas-pressure welding machine of GPW-1200,which is widely used in the rail exchange by each domestic railway administrations,has the control functions of flexible gas control,flexible oscillation of the heater,oil pressure control,welding process control,cooling process control and normalizing process control with PLC and its corresponding modules as the control core.According to the welding requirements of the high speed rail,the control system realizes the control of the gas-press welding machine and avoids the influence of human factors.The field application shows that it can apply to working condition of the rail off-line welding,rail on-line welding and rail welding repair with the good and stable rail welding quality.