This report is concerned with statistical analysis on long-term measurement of wave induced load of naval ships. We have analyzed wave-induced vertical bending stresses at midship deck and wave conditions measured by 12 naval ships which are equipped with Ship Motion Analyzing Computer System (SMACS) over a period of 84 years. We have introduced contribution rates between wave period and wave height on long term distribution of wave induced vertical bending stress in each stress revels and contribution rates between wave period and heading angle between ship and wave direction on the long term distribution. We derive the following conclusions. (1) When the range of the probability of exceedance in the long term distribution are from 10^-1 to 10^-2, the contribution rates between wave period and wave height and the rates between wave period and heading angle widely distribute over the wave conditions and heading angles. (2) For the range of the probability of exceedance from 10^-4 to 10^-8, the contribution rate is centered at a wave condition and a heading angle. The condition equals to the broad sense of resonance when the peaks of both the response amplitude function of the wave bending stress in regular wave and wave spectra are superimposed.