Block-matching motion estimations are used for the moving object tracking in video wildly. Although effective, traditional estimation algorithms, such as the full search, the three step search, the cross search, the new three step search, the diamond search, and so on, are either complex or time-consuming. In order to speed up the motion estimation, this paper presents an improved estimation algorithm based on the cross search and the diamond search algorithm according to video frame temporal properties. Experimental results show that the algorithm presented in this paper is more effective.