In the video scene, the technique on tracking multiple targets, such as tracking group of people through occlusion, is still challenging. In this paper, we present an algorithm for multiple targets tracking system. We discuss the behavior of the moving objects with adaptive search method. Several cases are classified, including the no match case, only-one match case, split case and occlusion case respectively. With this system, we can track the moving people in successive frame by object boundary box and velocity without color cues or appearance model. Even though people are interacted with each other or the occlusion is caused by other foreground objects, the proposed algorithm can still perform well. Furthermore we consider the people movement with respect to the distance with the camera as an adaptive search range to deal with the condition. As the foreground is similar to the background, the proposed algorithm can still solve the problem on the detection error.