Abstract: Objective The unsteady excitation forces generated by the rotation of the rotor consist of axial and circumferential components, which respectively affect the vibration and noise characteristics of the vehicle structure and the operational stability of the shafting system. Therefore, controlling the excitation forces is of vital importance for improving the vibration, noise and safety of the vehicle. Methods This paper selects a pump-jet propulsion model composed of a suboff boat stern-mounted acceleration tube, a 5-blade stator, and 4119 blades. Using the CFD method, it discusses the combined influence of the presence or absence of the stator on the excitation force of the rotor. Based on this, it explores the regulatory laws of the stator-rotor spacing and the circumferential bending degrees of the blades on the amplitude-frequency characteristics of the excitation force, and combines the flow field structure analysis to reveal the underlying mechanism.ResultsThe results show that the stator in front will enhance the non-uniformity of the inflow field of the rotor, resulting in a significant increase in the amplitude of axial and circumferential excitation forces. New high-frequency main peaks appear axially, and the circumferential excitation force is dominated by twice the blade frequency. The amplitude of the excitation force varies non-monotonically with the distance between the stator and rotor, decreasing first and then increasing. At medium spacing (0.2D to 0.4D), the axial and circumferential excitation force amplitudes are generally at a lower level. The circumferential bending degrees of the stator, by changing the distribution of the low-pressure area at the blade tip, causes the main frequency of the axial excitation force to shift to the high-frequency range. The amplitude of the circumferential excitation force decreases first and then tends to stabilize, and lower than that of the straight stator condition. ConclusionThe research results show that after the introduction of the Pre-installed stator, the axial thrust of the rotor increases, which is beneficial to improving the propulsion performance of the vehicle. However, it will increase the amplitude of axial excitation fluctuations, which has an adverse effect on the vibration performance. By optimizing the stator-rotor spacing and circumferential bending degrees, effective reduction of both axial and circumferential excitation pulsations can be achieved. Simultaneously, the frequency migration characteristics of the excitation force are regulated to mitigate low-order resonance risks and suppress harmful high-frequency spikes.