To solve the shortage of setting load of hydraulic support, this paper puts forward a computer simulation method. The reason for the shortage of setting load is firstly analyzed by simulating the pressure curve of prop’s lower chamber and the displacement curve of movable prop. It can be found that even prop lower chamber is supplied with fluid continuously, the pressure won’t reach to the pressure of pumping station, and the setting load also can’t be achieved. Secondly, the principle of auto-pressurized guarantee equipment for setting load is present. Only acting on one displacement, the pressurized valve can reach the pressure of pumping station. Simulation result also indicates that it can meet the requirement of setting load in a short time after the top beam reaches to the roof.