Compound control is a common method to reduce the tracking lag error for ship radar. However, the use is limited.The speed information of tracking target needs to provide. A new method of dynamic lag compensation based on positive velocity feedback for ship radar is proposed. In the absence of speed signals, the positive velocity feedback tracking link with lowpass filter is paralleled in the speed loop. The high frequency error component is filtered by the lowpass filter. The low frequency segment of the logarithmic amplitude frequency is improved obviously. Through the experiment, the new method based on positive velocity feedback reduces the speed error and acceleration error, and the radar tracking accuracy under marine dynamic environment is improved significantly.