Abstract: Lognormal random process model of fatigue crack propagation is usually used in the reliability and damage tolerance analysis.Basing on the model, a new method of evaluating the auto correlative parameter in usual stationary normal random process by the experimental data is established.By using this method, the value of the correlative parameter can be evaluated directly on the basis of the experimental data.At the same time, the confidence interval of the parameters is obtained by using Monte-Carlo method.At the end of the paper, a numerical example is given.In this example, a group experimental data of the specimens with fastening holes under pseudorandom spectrum loading, that obtained 237 data points, is used to determine the value of this correlative parameter.