High-speed flier velocity measurement is one of the key technologies in investigating collision sites on the surfaces of spacecraft structures impacted by high-speed space debris. We have designed and constructed an optoelectronic system to accurately determine the average velocity of a flier impacting on a spacecraft structure. The system is based on two parallel laser screens, which are crossed by the fliers before impact. This system utilizes scattered light as the start and the end signal to measure the time of flight between the two screens. A wideband optical sensor has been designed and evaluated, and an electronic circuit is used to accurately record the time of flight and calculate the velocity. Experimental results show this system is adequate to measure the velocity of a flier larger than 100 µm, in the range from 0.1 to 10 km/s, with accuracy better than 1.3%, and with low cost, simplicity, and high reliability.