Abstract: Objectives This paper aims to address the prominent issue of blade pass frequency excitation in centrifugal pumps used utilized in Ships. Methods A centrifugal pump of the same type utilized in ship is selected as the research object. A combination of numerical simulation and experimental testing is employed to investigate the internal flow and excitation in the pump. The original impeller is optimized, and a novel design concept of a composite impeller based on splitter blades is proposed. By comparing the steady flow field and unsteady performance before and after optimization, the underlying optimization mechanism is revealed, and the optimization effect is experimentally validated. Results The results show that the composite impeller can reduce the blade load on long blades and improve the uniformity of the outlet of the impeller. The standard deviation of the relative velocity at the impeller outlet of the composite impeller model is reduced by 5.9% compared to the conventional impeller, and by 1.67% compared to the conventional splitter blade impeller. Additionally, the composite impeller effectively mitigates the overall pulsation intensity caused by unsteady flow within the pump. Notably, pressure pulsations and radial force fluctuations at the outlet of impeller are significantly reduced. Specifically, the circumferential average amplitude of overall pressure pulsations at the outlet of impeller decreased by 47.8% compared to the conventional model, and decreased by 21.7% compared to the conventional splitter blade. Moreover, the blade frequency excitation force is reduced from 0.42 N to 0.04 N compared to the conventional model. The composite impeller demonstrates significant potential for suppressing blade frequency excitation, offering engineering value, experimental results indicate that the vibration intensity at the machine feet of the composite impeller model decreased by 92.4% compared to the conventional impeller model and decreased by 53.9% compared to the conventional splitter blade. Besides, the total vibration level in the low-frequency band is reduced by 3.25 dB compared to the conventional model and 0.97dB compared to the conventional splitter blade. Conclusions The design concept of a composite impeller based on splitter blades can further reduce the fluid-induced excitation in centrifugal pumps compared to conventional splitter blades. This research provides valuable references for the design of low-vibration and low-noise centrifugal pumps.