A comparative study is made on seismic design of port and harbor structures based on Chinese code, US guidelines and Japanese standards as well as guideline of International navigation association. This is the third of the series papers and the method for classification of site, evaluation of subgrade liquefaction, calculation of dynamic active and passive earth pressure acting on the structure in these codes are analyzed. It is shown that the methods for classification of site in these codes are similar but with different numbers. For evaluation of subgrade liquefaction,two step methods are used based on geological time, clay content and SPT counts in Chinese code. Soil shear stress method under earthquake excitation is adopted in US guideline. In Japanese code, a set of parameters based on uniformity coefficient, SPT, equivalent peak acceleration of ground motion and triaxial test are used for evaluation of subgrade liquefaction. For calculation of dynamic earth pressure, the Mononobe-Okabe equation or its modified formats are used in these codes.