The invention provides a water turbine operation state judging method based on a wavelet theory. The water turbine operation state judging method comprises the following steps that 1, denoising is conducted on a pressure pulsation signal by utilizing wavelet transforming, a pressure pulsation reconstruction signal is obtained, and the pressure pulsation reconstruction signal is divided into eightlayers and nine waveforms of different frequency bands are obtained; 2, the magnitudes of signal energy of the corresponding frequency bands are expressed by adopting standard differences of the pressure pulsation signal of the various frequency bands, the pressure pulsation reconstruction signal is calculated by utilizing a wavelet energy dimension, namely an inner product theorem, and energy corresponding to the various frequency bands from the low frequency to the high frequency is obtained; 3, the percentages of the energy corresponding to the various frequency bands and accounting for thetotal energy are calculated; and 4, an operation state where a water turbine is located is judged according to the energy corresponding to the various frequency bands and the percentages of the energy corresponding to the various frequency bands and accounting for the total energy. The water turbine operation state judging method has important significance for analyzing a failure state of operation of the water turbine.