The configuration and working principle of hydraulic system of flash butt welder were presented,and the mathematic model of hydraulic system of flash butt welder was established.The control model based on two-class fuzzy self-adjustment Proportion-Integral-Differential (PID) was introduced by aiming at the top-forging stage of the flash butt welding.The First-class fuzzy PID control was used for benchmark access,and the second-class for simultaneous access,the PID parameters were adjusted in real time to achieve simultaneous movement of the system.The control methods are effective in reducing the synchronous dynamic error of pressure on the two systems.