Corrosion is spatially distributed over RC structures due to several factors, such as different environmental exposure, concrete covers, and concrete qualities. Ignoring the effect of spatial variability is a drastic simplification for the reliability assessment of corrosion-affected RC structures. In this paper, a novel approach is established to assess the reliability of RC girders using finite element (FE) and probabilistic analyses considering the spatial variability of steel corrosion. An experiment was conducted to study the effect of current density on the spatial steel corrosion of RC beams. In the FE model, the spatial variability of steel corrosion was modeled by Gumbel statistics deduced from the experimental data. The results of FE analysis show that using the Gumbel distribution parameters derived from the steel weight loss data associated with higher current density cannot reproduce the non-uniformity of corrosion distribution, leading to an underestimation of flexural failure probability of RC girders.