Abstract: Elaborated in the article are the main aspects of the PID controller,covering the control principle,calculation method as well as the parameter selection steps,etc.,and how to use it to control operation of the tube hydrostatic test.The actual operation practice demonstrates that the said control system is capable of making the testing machine well perform such functions as quick pressure-boosting,eliminating any pressure fluatuation in the period of duration,and speeding up operation cycles and enhancing testing accuracy,etc.,having met all the control requirements of the tester.