<p>Oil film lubrication state is crucial for ensuring the efficient, stable, and enduring operation of axial piston pumps. However, the impact of vibrations during the operation of piston pumps on the oil film state remains unknown. Currently, the prediction of oil film state largely overlooks the influence of vibrations on the oil film state of the piston pair. This paper aims to study the impact of the vibration characteristics, load characteristics, and different stiffness dynamics parameters of piston pumps on the oil film thickness. A fluid-coupled model of the piston pair was constructed considering the relative motion of components within the piston pump; a system dynamics model was built considering the multi-degree-of-freedom motion state of the piston pair, and the model’s accuracy was validated using a single-piston test rig. The experimental measurements of oil film thickness were slightly less than the simulation values, while the peak pressure values were higher than those solved in the simulation. The pressure of the oil film and its thickness showed a non-linear negative correlation. Based on the dynamics model of the piston pair, the effects of piston pump vibration characteristics, load characteristics, and friction pair stiffness on oil film thickness were solved. This provides a foundation for developing piston pumps with more stable and robust oil film states.</p>