In order to track extended object more precisely, a high-precision extended object tracking method is proposed based on maximally stabel extremal regions (MSER) feature, according to binarization with sampling multithreshold, the MSERs are detected in a region of extended object, if area change rate of MSER meets centroid precision condition, the MSER is picked out. And MSER in next frame are extracted and matched with the MSER in previous frame, the centroid of the MSER matched is next tracking position. Experimental results show that the proposed tracking method can improve the stabilization and precision of extended object tracking, if area change rate of MSER meets the certain condition, the tracking precision is better than 0.1 pixel, and the time consumption reduces by 3/4.