Diesel excitation signal and vibration acceleration signal have intrica te non-stationary characteristics, and the characteristics of these excitation sources have important significance to fault recognition and condition monitoring . Research on the characteristics of these excitation sources is the base for other further studies. Based on the theory of cyclostationarity, the analysis method for diesel excitation sources cyclostationarity is discussed; then the reason of diesel excitation sources exhibited cyclostationarity is analyzed and valida ted by simulation signal; the experiment for measuring excitation sources of valve slap and piston knock from the characteristic of diesel is designed and the strain of valve and piston are got by the experiment; at last, the cyclostationar ity of excitation sources is got through the theory analysis and experiment result calculation. The result indicates that the cycle frequency of the diesel excitation sources is the half frequency multiplication of rotation frequency.