Nowadays, reinforced concrete is widely used as the material on building structures. It has perfect combination with tenacity of reinforcement and compression of concrete. The corrosion causes volume of reinforcement expanding, and the main factor which affects durability of concrete structures is the rusty reinforcement. Concrete has good compression but it doesn't have well tenacity. Therefore, concrete's tension crack, and cause the concrete's surface peeling. The diffusion of chloride ion is the main reason cause reinforcement corrosion. Therefore, the diffusion degree of chloride ions is used as the standard to evaluate reinforcement concrete structure's life. The diffusion of chloride ion is the important standard for researching reinforcement concrete structure's life. And many experiments and study theories are based on Fick's diffusion second law. Although it could apply to predicate reinforcement concrete structure's life, it still not established the complete theoretical system. The experiment and theory revised of Fick's diffusion law is limited in the condition of one-dimensional so far, and calculate the diffusion coefficient of chloride ion. In the limit of experimental analyses for modifications of Fick's diffusion law, this study will apply two-dimensional diffusion advancing model of finite thickness.,