High power electric semiconductor device is the foundation and core of the power electronics industry. As the production volume of power semiconductor devices are more and more big, power and voltage level is more and more high, the requirements to test efficiency and test quality are increasingly high. Pressure fixture is necessary for the test of high power semiconductor device. So, it’s necessary to develop high power semiconductor device test pressure fixture which has high efficiency, low cost and advanced technology. The technology that electric proportional valve was used to control the pressure of the gas-liquid pressurized cylinder was adopted to design a novel pressure fixture. Experimental results indicate that the proposed pressure fixture has good accuracy and linearity.