The study of elastomer collision processes is important for cushioning and vibration damping applications，but it is difficult to measure with general equipment because of the presence of rebound phenomena and the complexity of the process. A frequency-shifted photon Doppler velocimetry（PDV）using two laser sources is proposed to study the collision process of elastic projectiles. The magnitude and direction of velocity are obtained by analyzing the beat frequency signal，which is generated by the reference and signal beam provided by two lasers. The experimental results show that the velocity of the projectile decreased to zero within 0.1ms after impacting the steel plate，and several round-trip motions occurred 1ms after rebound.Errors due to laser frequency instability are reduced by monitoring the frequency difference between the two lasers.