The characterization of a triaxial piezoresistive high-g accelerometer by a Hopkinson bar and a data processing method are discussed. After fixing the accelerometer on the end of a calibration bar, the projectile launched from a barrel strikes the calibration bar at a high speed. The impact propagates in the calibration bar in the form of stress wave, which is recorded by a strain gauge fixed in the middle of the calibration bar. The sensitivity of the accelerometer can be obtained by comparing the output of the strain gauge and the integral of the accelerometer output. Using this method, the sensitivities of the Z-axis element and X-axis element of a monolithic triaxial piezoresistive high-g accelerometer is characterized by (2.18 μV/g)/5 V and (2.15 μV/g)/5 V, respectively. The test results are coincident with the previous results by dropping-bar test system,which shows that the characterization system and the data processing method used in this paper are reliable.