Abstract: Oil bearing is usually prepared by powder metallurgy process, which has the characteristics of self-lubrication, lightweight and near net shape forming. It has significant technical advantages in the current situation of mechanical products pursuing high performance, low energy consumption and environmental friendliness. For exploring the influence of seepage and pressure diffusion on the oil film lubrication performance of oil bearing, the seepage lubrication model of two-stage hole oil bearing system was established. The oil film distribution on the friction surface and the pressure diffusion behavior in the two-stage hole were studied. The effects of the variable obliquity and surface permeability on the oil film lubrication performance were analyzed. The main purpose of the study was to reveal the interaction between fluid seepage and pressure diffusion in two-stage porous structure. Results showed that the hydrodynamic pressure was generated in the convergence zone of the friction face. From the friction face to the bottom of the bearing, the fluid pressure gradually diffused to the matrix, the pressure action area increased and the pressure value decreased during the oil pressure diffusion process. The lubrication performance of oil film became better with the increase of obliquity or the decrease of surface permeability. Reducing the surface permeability could decrease the seepage and diffusion effect of oil into the porous matrix in the oil film area, which was conducive to increasing the hydrodynamic pressure of oil film on the friction interface. The lubrication performance of two-stage oil bearing with dense surface was better than that of single-layer oil bearing. Under different surface permeability, the effect of obliquity on friction coefficient was significantly different. Under the calculation parameters in this paper, when the surface permeability was less than 7 ×10⁻¹⁵ m², the friction coefficient decreased with the increase of obliquity. While when the surface permeability was higher than 7 ×10⁻¹⁵ m², the friction coefficient increased with the increase of the obliquity. At lower surface permeability, the hydrodynamic pressure of oil film between friction interfaces increased with the increase of the obliquity. And the lubrication performance became better. At the same time, the seepage and pressure diffusion effects of oil film into the pores of bearing matrix were enhanced, which would hinder the improvement trend of the lubrication performance to a certain extent. When the surface permeability reached a certain value, the bearing capacity of the oil film hardly changed with the increase of the obliquity, and the friction coefficient of the oil film increased with the increase of the obliquity. Under different obliquity and surface permeability, the seepage behavior of oil in porous bearing interacted with pressure diffusion, and finally changed the lubrication performance of oil film. The research provided a theoretical basis for clarifying the lubrication mechanism of oil bearing.