In the explosive detection, explosion impulse is a key parameter. The peak value and impulse of the explosion generation when they are in the air are important parameters, and it is an important index to measure the effect of blasting and kill, especially ammunition damage. A high accuracy velocity device work on falling bodies was given for the measurement needs of initiating explosive devices based on the current measure technique. For keeping the synchronization of light source and the hammer speed, double aperture slit was used in the device. The infrared transmitter, infrared receiver array and the circuit antijamming were designed to keep the device working in harsh environments such as strong electromagnetic fields. The system can give the measured data, and realize the multiple sets of data automatically and continuously. The impulse measure result was compared between chamber column and this method. The measurement accuracy is greater than ± 1%. The results prove that this test device can work stable and reliable.