Abstract: Cavitation is one kind of complex multiphase flow. Unstable cavitation flow can often induce a high amplitude of pressure pulsation, leading to the vibration of the pump body inside the centrifugal pump. A threat can also be posed to the safety and stability of pump operation. This study aims to explore the variation in the radial force and the pressure pulsation of the impeller, as the cavitation developed. A closed centrifugal pump was taken as the research object. Unsteady numerical simulation was carried out to investigate the cavitation flow in the centrifugal pump under a given flow rate. The homogeneous Eulerian-Eulerian two-fluid model was used to simulate the cavitation flow. Two-equation SST (shear stress transmission) k-ω model was adopted as the turbulence model to close the URANS (unsteady reynolds averaged navier-stokes) equations. The Schnerr-Sauer cavitation model was used to solve the volume fraction of the vapor phase. The reliability of the model and numerical simulation was verified to compare with experimental values. A systematic analysis was made to determine the influence of vapor bubbles on radial force and pressure pulsation. The research results indicated that the time-averaged radial force on the impeller first slightly decreased and then suddenly increased as the cavitation developed. The turning point was observed in the condition that the sheet cavitation appeared near the shroud. Furthermore, the time-averaged radial force reached as high as 60.5 N under complete cavitation, which was 1.4 times higher than under non-cavitation. And the peak value of radial force reached the maximum of 120 N, which was 1.69 times that of no cavitation stage. The high amplitude radial force caused the pump body more prone to instantaneous large vibration. The presence of bubbles disrupted the symmetry of pressure distribution, resulting in a polygonal distribution of radial force. The frequency of radial force variation was dominated by the impeller rotational frequency and its multiplication under different cavitation states. Once the cavitation was developed to the critical value, there was no variation in the amplitude of radial force corresponding to the impeller rotational frequency, while the amplitude of its multiplication increased only. When the net positive suction head was 1.9 m, the amplitude of radial force corresponding to the impeller rotational frequency was 41 N, which was about 1.4 times that under non-cavitation. The amplitude of radial force was 10 N corresponding to the sub-frequency of 2 times the impeller rotational frequency, which was 1.7 times that under non-cavitation. The influence of the breaking of vapor bubbles on pressure fluctuations shared a certain degree of global significance. This influence also depended on the relative position of the monitoring points and bubble clusters. The pressure coefficient and standard deviation were basically 0 when the monitoring point was located inside the bubble cluster. There was a significant increase and then a decrease, as the vapor bubbles were broken and aggregated when the monitoring point was located near the bubble clusters. The pressure wave generated by the breaking of vapor bubbles was also found downstream along the flow direction. The main frequency of pressure pulsation at each monitoring point was the impeller rotational frequency under different cavitation. The slow evolution of bubble clusters in the impeller induced the low-frequency pressure pulsations of 0.5 times the impeller rotational frequency during the complete cavitation. Consequently, the main frequency amplitude of radial force in the pressure pulsation was more suitable for evaluating the development of the cavitation flow field. The findings can also provide theoretical references to monitor and identify the cavitation in centrifugal pumps.