[Show abstract][Hide abstract] ABSTRACT: The TBD algorithm based on dynamic programming is an effective method for detecting dim target. But the DP process during the multi-frame integration causes the expansion of targets and strong noise which may produce a large amount of false targets. To reduce them, a new discrimination method which takes advantage of the feature of trajectory is proposed in this paper. The false alarm caused by noise reveals strong randomicity on its trajectory which is different from that caused by true target, and the new method based on the statistics of different level direction histogram can be used to reduce false targets caused by noise. Moreover a new concatenated discrimination scheme of SDH+LEV is proposed. The simulation indicates that the discrimination method of SDH is good for reducing false alarms caused by noise and preserving real targets at the same time. The concatenated discrimination scheme can delete false alarms caused by noise effectively.