In order to increase the loading capacity, reduce the friction and wear, prolong the life span of the port plate pair of the low-speed and high-torque seawater hydraulic motor, bionic non-smooth surface port plate with six kind of different dimple concaves has been conceived. Numerical simulation method has been applied to calculate the pressure distributions and loading capacities of the fluid film between the port plate with bionic non-smooth surface and end surface of motor rotor, the influence of the depth of dimple concaves, the form of dimple concaves and the rotor rotating speed on the loading capacities of the port plate pair has been analyzed. The results indicate that the loading capacities of bionic non-smooth surface port plate pair with the same rotating speed increase with the increasing depth of the pits. Under the same rotor rotating speed, the loading capacities of bionic non-smooth surface port plate pair with circular conical pit, square conical pit, circular hemispherical pit decrease almost linearly and slowly with the increasing depth of the pits. Under the same rotor rotating speed, the loading capacities of bionic non-smooth surface port plate pair with circular cylindrical pit, square cylindrical pit, triangle cylindrical pit decrease with the patterns of hyperbolic curve, and when the depth of the pit are equal and greater than 0.5mm, the loading capacities almost have the same values, but much less than the values of with circular conical pit, square conical pit and circular hemispherical pit. The work of the paper such as bionic non-smooth surface effects has some references for improving the loading capacity and anti-wear performance of the key tribopairs such swash plate/slipper, port plate/cylinder block and piston/cylinder block of the high pressure axial piston pump used in aircraft so as to promote the reliability and increase service life of the axial piston pump.