The work aims to study the failure mechanism of railway relay contacts. The electric relay electric life test was carried out under the direct current condition to automatically recognize the contact area between the static contact surface and the moving contact. 3D topography scanner and SEM were used to scan the contacts, the plane reference surface was selected, the contact surface roughness parameters were calculated, and the surface topography changes of the contact surfaces were analyzed. Elemental analysis was performed on the ablated surface of the contact to investigate the microstructure and failure mechanism of the contact surface. The Sa/Sq value less than 0.8 indicated a random surface. For Sa/Sq (static) =0.246