Acquisition of real-time speed during ammunition penetration has great significance on ammunition position judgments and burst point control. In this paper, the principle of a velocity measurement device with double piezoelectric sensors and timer as main components was presented. According to different pressure variation when the ammunition is passin g through different media, with reference to other relevant principles, the penetrating speed when the ammunition is passin g through different media was determined, by which the previous velocity measurement principle was improved. Verified by simulation, the system is proved to be reliably useful.