Aimed at the problems of that the present pressure sensors can not adapt high pressure testing in high pressure、high temperature and high impact environment, a transient ultra-high pressure piezoresistive sensor was provided. The sensor works with the Wheatstone half bridge principle, and uses the well-piezoresistive alloy manufactured by SiGeMnCu as the sensing element material. By improving the production process and assembly method, the sensor can realize 0～800MPa dynamic pressure testing in transient high pressure and high temperature environment. The comparative analysis shows that the nonlinear error of the sensor is not greater than 0.5% at the high, low and normal temperature. The sensor has the advantages of high sensitivity, small volume and flexible installation. It can be widely used in the pressure testing and research of high pressure gun and airtight exploder device.