Abstract: The area where our ship can attack target by torpedo but the target cannot attack our ship by torpedo is named torpedo advantageous attacking area of ship, or the torpedo disadvantageous attacking area of target. The research into the torpedo advantageous and disadvantageous attacking areas is to solve the problems of underwater threat judgment and torpedo defense for submarine and surface ship. Based on the analysis of torpedo hitting factors, it is concluded that there is torpedo advantageous and disadvantageous attacking areas around ship. By the further analy sis for the advantageous and disadvan tageous attack ing areas of a straight running torpedo, it is found that the seareas are directly correlated with the mutual speeds, torpedo speed and effective hitting range. The research result is expected to lay the foundation for eliminating the enemy torpedo advantageous attacking area.