A port steel structure under marine environments often shows structural performance degradation due to loss in steel cross section caused by corrosion. Therefore, repair and strengthening methods that have high potential for use in the sea are needed. In this paper, a conventional FRP bonding method was focused on to investigate its applicability to port steel structures. CFRP strand sheet was bonded with epoxy lining material that is hardened in the water on a steel pile having a purposely decreased section to simulate the real corrosion status. Bond tests on steel plates and bending tests on corroded steel pipes strengthened by CFRP strand sheet were carried out. As a result, it was proved that the bonded CFRP strand sheet through the particular epoxy lining material can reduce the stresses efficiently in corroded steel piles. The effectiveness of the proposed strengthening method was demonstrated. ; Department of Civil and Environmental Engineering