The invention discloses a rotating speed control system and method of water hydraulic motor. The method comprises the following steps that 1, fuzzy control is used for overcoming the defect that because a traditional control mode is not high in control precision, the traditional control mode cannot adapt to the variable quantity and non linearity of a water hydraulic system; 2, feedforward is carried out by utilizing target rotating speed, and the rotating speed fluctuation of the water hydraulic motor is compensated in advance according to the total volume efficiency feedback mode of the system; 3, the difference between the theoretical rotating speed of a servo motor and the actual rotating speed is fed back, a local small closed loop is formed on the control of the rotating speed of theservo motor, and the precision of the rotating speed control of the servo motor is improved; 4, the interference components in the flow signals are stripped based on a multi-resolution analysis theory, and then the signals are reconstructed; and 5, wavelet transformation is carried out on the rotating speed signals to reduce or eliminate quantization errors in the rotating speed information. Thecontrol precision of the rotating speed of the hydraulic motor is high, and the response speed is high, the anti-disturbance capability is strong, and the rotating speed of the water hydraulic motor is smooth.