The motion template algorithm in complex environment cannot extract the region of moving objects accurately, and relying on the selection of inter frame spacing it cannot achieve good effect when detecting slow moving target. We propose an improved motion template algorithm. Firstly, we adopt the Canny operator as well as the contour information to extract the waterfront boundary line in the input video sequences.  Secondly, we divide the motion history image (MHI) into two parts along the waterfront boundary line so as to eliminate the interference of the moving target on the water’s edge. Then, morphological manipulations on water area of the MHI are used to eliminate non-target objects in the background. Finally, we obtain the maximum width and height of the external rectangle of the contour by detecting the ship contour from the processed motion history image. The external rectangle of the contour is reconstructed according to the current obtained coordinates of the ship. Experimental results show that our method can achieve accurate and real-time ship detection and tracking under complex water environment.