In order to improve the performance of estimation in radar-photoelectric system,we proposed a track fusion algorithm with Unbiased Converted Measurements (UCM) of velocity.First,with the information of radial velocity provided by radar and angle velocity supplied by photoelectric system,we obtained the UCM of velocity in Cartesian coordinate and analyzed the statistical properties of UCM errors.By using the information of velocity,we provided a synergistic fusion algorithm based on sequential filtering.Simulations show that the algorithm with UCM of velocity provides a better performance of tracking and improves the convergence rate of velocity estimation.Moreover,the results also offer some beneficial references for track initiator and primary assessment of threat.