In this paper, surface topography characteristics of electrochemical mechanical finishing (ECMF) for steel was investigated. The scanning electron microscopy (SEM) was used to observe the surface topography. And the microcosmic geometry parameters were measured by Talysurf SLI2000. Compared with original surface, the surface topography characteristics of the workpiece machined by ECMF have been analyzed with altitude density function (ADF) and auto correlation function (ACF). The results show that there exist periodicity component in surface profile before and after finishing. The auto correlation curves of ECMF surface have a smaller average period compared with grinding surface. The low-frequency component and the mean ripple peak distance of original surface profile are obviously decreased. Furthermore, the ripples and peak density are increased, and the surface roughness Ra is decreased from 0.231μm to 0.023μm. The results indicate that surface quality, material ratio of the profile and wear resistance machined by ECMF are improved obviously.