To improve the accuracy and efficiency of fatigue damage calculation of ship accounting for slamming load, two calculation methods are investigated. Firstly, the stress is obtained by a time-domain calculation method, and the damage at the location of interest is obtained by the rain-flow counting method and the Miner’s linear cumulative damage theory. Then a nonlinear load influence coefficient is calculated according to the China Classification Society guidelines, and the stress response transfer function is corrected according to the spectral analysis method. The next step is to calculate the fatigue damage considering slamming load. Secondly, the nonlinear load influence coefficients at five key hull sections are calculated. Then, the nonlinear influence coefficients at the location of interest are obtained by interpolation and multiplied by the spectral analysis of linear fatigue damage to obtain the fatigue damage considering the slamming load.