A new multi factor modified model of chloride diffusion in concrete was formulated, in which the dynamic correlations between chloride diffusion capacity and frost damage, surface scaling of concrete structures were taken into account. This modified model was verified and applied on basis of field data from practical engineering of an urban overpass and Jiaozhou bay subsea tunnel. The result indicates that the prediction is exactly consistent with the field chloride content under salt frost environment. Meanwhile, the modified model is very simple and convenient for engineering application.