Chloride attack has been identiﬁed as one of the most important factors initiating the corrosion of reinforcing bars. Chloride penetration into the concrete is generally recognized as a diffusion-controlled process. Material properties of the concrete structures are widely recognized that it is of intrinsic randomness, and it is an urgent task to develop a stochastic analysis method for chloride diffusion. Firstly, a deterministic boundary element method with new time marching scheme is developed and described. The diffusion coefficient is described as the random field and discretized based on the local average theory. In order to conduct a stochastic analysis, combining the Monte-Carlo simulation technique with the proposed BEM, the Monte Carlo stochastic BEM for stochastic analysis is proposed in this paper and used in numerical examples. Stochastic analysises presented in this paper provide basis for the reliability analysis of the durability of the concrete structures.