Changes in the operating conditions of the centrifugal pump cause fluctuations in the hydraulic load torque, which stimulates current in the motor stator when transmitted to the motor through the rotor shaft system. In light of the relationship between the operating conditions of the centrifugal pump and the stator current of the motor, the hydraulic load torque characteristics of the centrifugal pump under different operating conditions are analyzed through numerical simulation. The hydraulic moment changes periodically, its mean value increases with the increase of the flow rate, and the root mean square of the hydraulic moment pulsation intensity increases as the operating conditions deviate from the design conditions. Furthermore, theoretical analysis shows that the characteristics of torque are reflected in the motor stator current by power frequency modulation. Finally, the motor stator current is measured through experiments, the root mean square of the stator current is calculated, and the power frequency signal of the power grid is eliminated by the singular value decomposition method to realize the extraction of current characteristics for centrifugal pump running state. The results show that the root mean square of the stator current is consistent with the root mean square of the hydraulic load torque. The calculation of total harmonic distortion (THD) shows that it tends to increase as the operating conditions of the centrifugal pump deviate from the design conditions.