Abstract: This paper is to study the fault diagnosis to the water level regulator of the ship main condensers based on the analysis of wavelet packet-time series. During the process of the research experiment, four state models are set for collecting their flow signal. The signal can be decomposed and denoised by the wavelet packet, and through the time series analysis, the characteristic information is obtained and the fault can be diagnosed by the Euclide distance. The experiment indicates that this method is correct and valid.