High-speed flyer velocity measurement is one of the key technologies in simulating impact of space flyer driven by ground-based system. A non-contact velocity measurement system for high-speed flyer is developed, and the sources of measurement error and the way to improve the measurement accuracy are also analyzed. A high-power laser diode module is used as the light source, and a PIN photodiode is used as the photo-detector. This system utilizes lateral scattering light as the start and the end signal to measure the average velocity of flyers. Experimental results show that this system is adequate to measure the flyers lager than 100 μm, with the velocity varying from 1 km/s to 10 km/s. And its accuracy is higher than 1.8%.