Aiming at the problem that the accuracy of the fusion results of high conflict evidence in the classic D-S evidence theory is low in actual maritime situation analysis, a data fusion method to improve the D-S evidence theory is proposed. The evidence distance formula based on the law of universal gravitation is used to measure the degree of conflict between evidences, and the fusion results with larger conflicts are given a smaller weight, and the fusion is carried out through the identification of maritime weapons. The results show that the more obvious the evidence conflicts of this method, the greater the advantage; when the conflicts between the evidences are small, the fusion results are consistent with the classic D-S evidence theory, and have higher accuracy and stability.