In the aerospace domain, ultrasonic vibration-assisted nanosecond laser processing technology has been demonstrated to significantly reduce surface roughness by mitigating the heat-affected zone and surface defects during processing. This technology plays a crucial role in enhancing the fatigue life and corrosion resistance of aircraft components, thus ensuring their safety and reliability. The objective of this study is to investigate the effects of ultrasonic vibration and laser power on the nanosecond laser ablation process. Based on the principles of laser thermodynamics and ultrasonic mechanism, a thermodynamic model for fixed-point pulse ablation with and without ultrasonic assistance was established. The accuracy of the simulation results was validated through experiments. Microscopic morphologies of both nanosecond laser processing (NLP) and ultrasonic vibration-assisted nanosecond laser processing (UVNLP) were compared using simulation and experimental approaches. Results indicate that as laser power increases, the diameter and depth of ablation pits increase, surface roughness rises, the slope of ablation pits increases, and the rate of depth increase exceeds that of diameter. The introduction of ultrasonic vibration reduces pit diameter by 1.4–2.0 μm and surface roughness by 0.092–0.208 μm compared to conventional NLP, thereby significantly improving surface quality. This improvement is essential for extending the service life of aircraft components and reducing maintenance costs.