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In order to study the flow characteristics in centrifugal pump at design condition, the inner unsteady flow was simulated based on high-quality structured grid and rapid prototyping technology by using the commercial software CFX．The results indicate that the method of unsteady numerical simulation can accurately predict the performance parameters of the centrifugal pump with the test. The maximum deviation of head and efficiency are less than 4% and 3%, respectively. Impacted by the impeller-volute coupling, the pressure pulsation in volute centrifugal pump has strong periodicity, and the basic frequency is the blade passing frequency. There is a similar pressure field between the impeller passage inlet and the middle of impeller passage, but the pressure distribution near the impeller outlet has a significant difference. Significant secondary flow phenomena exist in the volute and move forward with the mainstream.