This report presents a result of authors' study on longitudinal strength of destroyer type ships. As the first stage, we examine the design longitudinal wave loads such as vertical wave bending moment and horizontal wave bending moment and totalize wave stress induced by them. The method of calculation is based on the concept of total system which has popular technique to predict the extreme value of wave induced loads and stress. As the result, the extreme value of vertical wave bending stress for the probability of exceedance Q =10^-8 shows a large value as much as the conventional strength calculation by supposing a trochoidal wave with a height equal to L /20. By using an approximate formula of extreme wave load for merchant ships proposed by Akita et al., the extreme wave load of destroyers are examined. The values can make good approximate with the formula. Regarding the above result, the standard values of wave load of the ships are proposed for the convenience of initial design.