Abstract: The paper presents a model of aero-engine load spectrum related to operation,and makes a statistic analysis for vertical overload factor spectrum of a fighter engine center of gravity.The model is proved reasonable.The results show that load spectrum related to operation can be described by Poisson stochastic processes,which are completely determined by four factors such as distribution of loading duration,distribution of loading arrival interval,frequency accumulation curve of loading duration and frequency accumulation curve of loading level crossing by Level Crossing Counting.The loading duration and the loading arrival interval yield exponent distribution.Based on the equivalent of the four factors,a simulation method for load spectrum related to operation is provided.As an example,the vertical overload factor spectrum of the engine is simulated.The results are satisfactory and show that this simulation method is correct.