According to classical similarity theory and the main characterization of durability of the marine prestressed concrete structures, the time similarity relationships between trial structures of indoor accelerated simulation tests in an artificial environment and the in-situ structures in the actual environment have been established by taking chloride ion diffusion coefficients as a linkage. Considering the chlorine salt corrosion environmental conditions in the Lianyungang port, the design of the homologous system of corrosion for artificial climate modeling is made. Simultaneously, two experimental beams with the same composition of materials and similar structural features are poured. And then a sample of concrete powder which is taken from the beams placed in the artificial climate modeling laboratory and in the Lianyungang port area is used for examination and tests on the concentration of the chloride ion by use of a rapid chloride ion detection method (i.e a RCT method). On the basis of the Fick’s second law of diffusion, the diffusion coefficients of the chloride ion are fitted by a software Matlab. The corresponding time similarity coefficients λt under the marine atmosphere are calculated. This method can provide the basis for prediction of the service life of the marine prestressed concrete structures and make a key step for engineering applications in the future.