Proportional coefficient, integral coefficient, and differential coefficient, as parameters for adjusting the dynamic response of the controller system, play an important role in the proportional integral differential (PID) control. In order to study the flow control characteristics of the forward bending centrifugal pump under the PID control, with constant flow rate as the control objective, the specific performance of PID parameters in different ranges and the control characteristics of each link are tested. The research results indicate that unstable oscillation in flow control of centrifugal pumps can cause motor start stop. Due to the limit up protection limitation of the frequency converter, a high proportion coefficient will not shorten the initial flow regulation rise time of the control, and will increase the overshoot and reduce stability, therefore, a lower proportion coefficient should be selected. The upper limit of overshoot caused by integral saturation is 33.50%. Continuing to increase the integral coefficient can shorten the steady-state time until the coefficient is too large and affects stability, leading to oscillation. If we try to avoid overshoot as much as possible and choose an integral coefficient of 0.5, the flow regulation will fluctuate and quickly stabilize near the target value after the initial rising stage, with a weak overshoot of 8.82% and a steady-state time of 7.4, which has the best control effect in testing. The flow advance regulation related to differential coefficient plays a weak role in the actual control, and does not significantly improve the fluctuation in the regulation process. Finally, based on the above conclusions, a reference is proposed for the optimization of PID tuning in the flow control of variable frequency centrifugal pumps.