Abstract: 250 MPa ultra-high pressure common rail fuel system was tested, the pressure fluctuation characteristics under different pressure and temperature conditions were obtained. Then, the pressure wave velocity and the total volume elastic modulus of the fuel and high pressure pipe were obtained according as the pressure fluctuation between the injector end and the common rail end. Finally, the calculation formula of the pressure wave velocity and the total volume elastic modulus were obtained for the injection pressure in the range of 180 to 250 MPa and the temperature in the range of 15 to 40℃.