Motion target detection and tracking is one of the most important issues in applied vision research due to its wide applications in many fields. In this paper

a difference image based motion detection algorithm

which results in the symbolic representations of motion targets via their outer rectangular bounds

is presented. Then according to the continuity constraint

motion targets are tracked through image sequence. Experiments show that this method is fast and feasible which can deal with the overlapping and timely missing problems of targets in tracking more properly comparing with other existing methods.