Abstract: To investigate the impact of cavitation flow within a pump-turbine runner on pressure pulsations and blade loading, unsteady numerical simulations were conducted under pump operating conditions using the MSST PANS model, covering a net positive suction head available (NPSHa) range of 1.71 to 10.01. After grid and time-step independence verification, the discrepancy between the simulated head and experimental results was less than 2.3%. When NPSHa exceeded the critical cavitation margin (NPSHc), the peak-to-peak pressure pulsation amplitude gradually increased from the flow channel inlet to the outlet, indicating that rotor-stator interaction is the primary cause of pressure pulsations. When NPSHa fell below NPSHc, cavitation flow within the runner led to a sharp increase in pressure pulsations, with the peak-to-peak value rising from 4.9% at NPSHc to 11.2% at NPSHa=1.71. Furthermore, the location of the maximum peak-to-peak pressure pulsation shifted dynamically. Under these conditions, cavitation induced fluctuations in the volumetric flow rate within the runner, resulting in flow disorder and the generation of numerous vortex structures. Regarding radial forces, within the range of NPSHa ≥ NPSHc, they remained largely unaffected by changes in inlet pressure, with relative fluctuations below 2%. However, when NPSHa < NPSHc, the dominant frequency of the radial forces shifted to a low frequency induced by cavitation flow, and the magnitude of the radial forces increased by approximately 6.9% to 21.1% compared to non-cavitation conditions.