To avoid equilibrium potential shifts in polarization curve test, based on anodic polarization current method, the critical polarization current density of steel corrosion was given as well as the corresponding empirical formula of corrosion current density. Reasonable explanation to equilibrium potential shifts was given by studying polarization curves characteristic of rebar in concrete before and after corrosion. The results show that anodic polarization current method can effectively distinguish steel corrosion, and the critical polarization current density is 0.2 μA/cm 2.