Extending Yang s [1] studies of fatigue damage determination in structures under stochastic loading, this study was developed using the same philosophy, besides incorporate a FFT routine to the power spectral determination, the Coffin-Manson method and Miner s rule, to structure damage determination. Two software were developed to apply this method. The first one realizes three basics functions: Data Acquisition: Recording real loading processes Analysis: Determination the statistical and spectral properties of the loading processes Random loading Process Simulation: Using Gaussian simulation method. The second software contain the routines necessary to life estimation using the Coffin-Manson method: peak and valley counting, rain-flow rule, damage and cumulative damage calculation. A computational processes were applied on loading processes found on correlated studies, and the numerical results were compared with their experimental one. At last, it was objected to studying the influence os spectral resolution and the number of iteration on life prediction, to find the best parameters to a good simulation.