Abstract: Based on the research on water level regulator of steam-power ship＇s main condenser, this paper picked up the relative energy eigenvector by using the convolution type of wavelet packet decomposition, built the stan dard fault database, and took Euclidean space range formula as criterion to identify faults. The experimental results show that this method can diagnose the typical faults of the water level regulator quickly and corre ctly. And this method can also decrease the blindness of the diagnosis and the maintainance.