The invention relates to a water turbine generator set monitoring device which comprises a computer, a data collector and a sensor set electrically connected with the data collector. The sensor set comprises a low-frequency vibration sensor, an electric eddy sensor, a pressure transmitter and a power transmitter. The low-frequency vibration sensor is used for measuring the vibration frequency and the vibration strength of a water turbine generator set fixing part. The electric eddy sensor is used for measuring the main shaft runout, namely the radial displacement, at the position of a three-guide bearing of a water turbine generator set. The pressure transmitter is used for measuring the pressure pulse of the interior of the water turbine generator set, the water heat differential pressure of an inlet and an outlet and the flow differential pressure. The power transmitter is used for measuring the active power and the reactive power of the water turbine generator set. The data collector is used for collecting measuring data of the sensor and transmitting the measuring data to a computer. Special analysis software in the computer is used for detecting and estimating the running state of the water turbine generator set. By means of the technical scheme, the working state of the water turbine generator set can be monitored in real time.