A length estimating mathod of ship target based on wide-band radar’s high range resolution profile (HRRP) is presented. The main process is as follows: firstly, the attitude angle of ship target is estimated based on radar track, and the features of the movement state are extracted; secondly, the integrity of HRRP is judged by the boundary amplitude; then the HRRP is aligned according to the adjacent correlation method, and the abnormal HRRP is removed; Finally, the ship target region of the interest area is segmented, and the ship length is calculated according to certain projection criteria. The method proposed in this paper has a high measuring precision and great engineering application value. The actual data show that the average error of ship length estimated is less than 10%.