To research the internal flow characteristics of a single-channel centrifugal pump, the computational fluid dynamics method is used in this study. Several monitoring points are set on the volute to analyze the change of pressure pulsation and radial force when the impeller rotates at different angles. The results show that the pressure pulsation in the single-channel pump volute is induced by the rotor–stator interaction and its harmonics. The monitoring points close to the separation tongue along the rotation direction of the impeller are more affected by the flow rate.