Abstract: This paper attempts to illustrate the law of corrosion fatigue with parameters of fatigue characteristics of test piece under sea water corrosion. A method of calculating corrosion fatigue life of the semi-submersible platform column is proposed. Applying the nth dimensional Airy wave theory, the pattern of random wave surface elevation is determined from the randomness of initial value. Analysis of the dynamic response of semisubmersible platform is made and a formula for calculating the coefficient of horizontal restoration of the mooring system is derived. The proposed method of calculating the fatigue life is to calculate the stress range and stres ratio of the stress cycle directly from the frequency spectrum of random stress. Some improvement of the Paris formula for determining the coefficient of fatigue load, fatigue frequency etc. is suggested through test of 16 Mn steel(national standard)in sea water environment, and prediction of corrosion fatigue life of semi-submersible platform column in South China Sea is made.