Abstract: Abstract: In order to improve the hydraulic design level of centrifugal pump, 4 indicators i.e. noise level at BPF (blade passing frequency), efficiency, head and shaft power were taken as criteria, and the matrix method was firstly used in pump design field to finish the multi-target optimization of a model pump. All the indicators were calculated by the combined CFD/CA (computational fluid dynamics and computational acoustics) method, which was based on Lighthill acoustic analogy. Efficiency, head and shaft power of the pump were obtained from the flow field calculation, and sound pressure level of fluid-borne noise was simulated by the computational acoustics from flow noise source. Vibro-acoustic interaction effect between the fluid and solid wall was not taken into account during the process of fluid-borne noise calculation. The effects of the variation of impeller diameter, blade inlet angle, blade outlet angle and blade outlet width on the 4 indicators were well investigated based on the L9 (34) orthographic experiment. Furthermore, the optimum plan was selected according to the weight of each factor from the simulation. After comparing the test results between the optimized impeller and the original one, it was found that the optimum model satisfied all the standards. The head was 2.5% higher than the original model, the efficiency was 3.8% higher than the original one, the shaft power was 3.3% lower than the original model and the sound pressure level at export was 1.2% lower than the original model at nominal flowrate. It was verified that the matrix optimal method combined with the numerical simulation in pump optimization was feasible. Within the reasonable range, the gap between impeller and volute tongue was no longer the most significant factor for flow-induced noise of the pumps. Moreover, the PIV (particle image velocimetry) method was used to compare the inner flow field of the 2 models and analyze the difference to find out why the optimal impeller could supply a better performance with low noise. Non dimensional velocity related to the same volute inlet radius was used to carry out the comparison. The results showed that there was no obvious "jet-wake" flow structure existing inside the optimization mode, the optimized impeller's maximum velocity was 6.7% smaller than that of the original prototype pump, and its range of low velocity area was larger than the original pump model. Besides, due to the decreasing of the diameter of impeller, the impeller-tongue interaction effects were also weakened. All of these were the main exact reasons for the phenomenon that the optimal impeller had a lower noise. The key to design an impeller with high efficiency and low noise was to keep a reasonable gap between impeller and tongue (or diffuser), and form a better control on the flow in the impeller channels by better blade shapes so as to weaken the wake pulsation at impeller trailing edge. The research provides the theoretical and technical references for the hydraulic design of the multi-objective optimization, and especially for the new type of non-overload centrifugal pumps with high efficiency and low noise.