In view of unresolved targets and high-speed start technology during ripple fire, muzzle velocity measurement is still difficult. The time-distance-frequency method based on the distinguishment of distance was used to distinguish multi-objective in this article. It can meed the unresolved targets demand for ripple fire. Infrared trigger combined with microwave trigger mode was used in this article. Continuous wave radar was used to designate muzzle, when projectile was ejected from muzzle, the received Doppler radar echo signal had a mutation. When detecting and locating the mutation signal, the time when the projectile leaving from muzzle was got. It can overcome the effect of flame noise. In the end, prototype schematic was given. It can provide the references for the final design for muzzle velocity test of ripple fired projectiles.