Abstract: A piston pressure device includes a gas concentration-regulating piston pressure device and a high temperature autoclave. In the gas concentration-regulating piston pressure device, the proportion and concentration of corrosive gases can be accurately adjusted, intermediate gases can be stored and filled into the high temperature autoclave according to experimental needs, and an actual corrosion process in oilfield is accurately simulated. Meanwhile, the corrosive gases can be supplemented in real time during the experiment, and dynamic gas distribution in a high-temperature high-pressure corrosion experiment process is realized.