Abstract: A three-dimensional wheel/rail adhesion numerical model under wet condition, which considers surface roughness of wheel and rail, was established to obtain the characteristics of wheel/rail adhesion at high speed. Based on the partial elasto-hydrodynamic lubrication (EHL) and elastic micro asperity contact theory, multi-grid method was employed as a numerical tool for solving the established model. The effects of train speed, axle load and surface roughness on the adhesion between wheel and rail were investigated, and then explained from the numerical aspects. The results show that the adhesion coefficient decreases with the increasing of train speed. It is also shown that the adhesion coefficient decreases with the increasing of axle load. Properly increasing surface roughness is benefit to the characteristics of wheel/rail adhesion.