As for the multi-sensor target decision-making system, with the affection of the opponent and the environment, the use of D-S combination rules in dealing with high conflict information will always arrive at a counter- intuitive conclusion. In this paper, an improved evidence combination rule is proposed. Firstly, conditional Boolean algebra distance is applied to define drop-falling distance, from which drop-falling similarity is deduced. Then, the credibility of evidence, as the weight of significance in evidence combination, is defined from the drop-falling similarity. Finally, the evidences are combined according to Murphy's combination rule. Both theoretic analysis and numerical examples confirm the validity of the proposed approach and the superiority to the existing methods in combining conflicting evidences.