Diamond search (DS) is an excellent fast block matching motion estimation (BMME) algorithm. In this paper, we propose an improved diamond search (IDS) algorithm, which revises the two search patterns of DS. The proposed algorithm is compared with several mainstream algorithms. The simulation results show that the proposed algorithm over DS can be up to 20% gain on speedup on average, while maintain the similar or even better quality, both objectively and subjectively. The proposed algorithm is also competitive with other fast algorithms.