Different carbonized concrete specimens were obtained by rapid carbonization test and their chloride diffusion coefficients were tested and calculated by rapid permeability test.The results show that there’s no obvious difference between chloride diffusion coefficient of totally carbonized concrete and that of partly carbonized concrete while that of non-carbonized concrete is higher than the former two.It can be concluded that there exits substantial benefits of reducing the chloride diffusion coefficient by concrete’s carbonizing; concrete’s carbonizing increases concrete’s density to some extent by reducing the porosity. The chloride diffusion coefficient of totally carbonized specimen is about 1/2 that of non-carbonized specimen. This paper also introduces a method by using pH device to measure the pH of different carbonization degree concretes and offeres the changes of the pH.