Corrosion fatigue test was performed by the use of plane bending fatigue tester in marine environment having various specific resistance from 25(natural sea water) to 5000.ohm.cm. It is in order to investigate the effects of marine environmental factor on the corrosion fatigue fracture of SS41 steel. The main results obtained are as follows; 1. The aspect ratio(b/a) of corner crack growing in natural sea water is lower than that in air. 2. The surface crack growth rate(da/dN) in marine environment is faster than that in air and da/dN delaies with the specific resistance increased. 3. The experimental constant m of paris rule [da/dN=C(${delta}$K)$^m$] decrease with the specific resistance decreased and the effect of corrosion in proportion to the specific resistance is more sensitive than that of stress intensity factor range(${delta}$K) under region II. 4. The accelerative factor(${alpha}$) in marine environment is about 1.1-2.7 and .alpha. is increase under the low region of stress intensity factor range(${delta}$K). 5. The electrode potential($E_0$) gets less noble potential with the specific resistance decreased.