Merge mode makes full use of the relation between blocks and their nei ghbors to significantly improve the compression of high efficiency video coding (HEVC).However,greater computati on complexity is introduced compared with the previous video coding standards,which will limit its practical applications.Checking all the merge mode candidates for the best one introduces new complexity to Merge mode.To reduce the complexity of Me rge mode,first of all,this paper analyzes the characteristics of rate distortion (RD) cost when depths and quantitive parameters (QPs) of the blocks are different,then proposes an adaptive method to reduce the complexity of RD-cost compution to get the best m erge candidate.As a result, unnecessary merge mode selection can be skipped and terminated.According to th e simulation results based on HM 14.0,conclusions are obtained that the proposed method can reduce about 15.38% encoding time with only 0.37% Bjntegaard delta (BD)-rate increase,while maintaining almost the same R D performance as the original HEVC encoder.