The friction and wear performance of the valve plate pair significantly affects the service life and reliability of axial piston pumps. Loading pressure during the running-in process is crucial to its contact characteristics, friction coefficient, running-in time, wear rate, etc. In this article, mixed lubrication modeling and analysis of the effects of loading pressure on tribological performance for valve plate pair were conducted. A finite element model was established using fractal theory and a coupled Euler-Lagrange method. Ring-on-block tests were conducted to simulate the movement and tribological properties of the valve plate pair during the running-in process. Running-in tests of the axial piston pump were carried out to detect the valve plate’s wear. Results show that the effect of increased loading pressure on the maximum contact pressure decreases gradually. The increased loading pressure can shorten the running-in time without increasing the friction coefficient. The wear mechanisms are abrasive wear and adhesive wear during the running-in process. This study provides a reference for the running-in test of axial piston pumps.