In the clinical application of left ventricular assist devices, flow rate is an important parameter, but flow meters are limited to be used because of it’s poor reliability. This paper proposes a new flow estimation method based on the working parameters of the motor for the CH-VAD blood pump developed by CH Biomedical, Inc. The blood pump system is disassembled into two modules: a motor and a centrifugal pump for analysis. First, the motor’s voltage, current, speed and duty cycle are calculated to obtain the output torque of the motor, and then the relationship between flow and torque at different speeds and viscosities is tested through experiments, and a fitting relationship is proposed. In the data of the two blood pumps, the goodness of fitting reached 0.9826 and 0.9829, respectively. The parameters obtained by fitting are used for verification. When the viscosity changes, the root-mean-square error of the estimated flow of the two blood pumps is 0.260L/min and 0.274L/min, respectively. It shows a high accuracy, while the fitting parameters of the two blood pumps and the estimation results are in good agreement, which proves that the flow estimation method can be used for CH-VAD blood pumps. Tests under pulsating flow show that this method is less affected by pulsation and can follow the actual flow waveform well.