To understand the deterioration mechanism of CFRP/steel interface properties under extreme hot and humid environment， 12 of CFRP/steel double lap specimens using Sika-30 adhesive were prepared. These specimens were immersed in simulated seawater at 70 ℃ for different time for tensile shear test. The results show that the failure mode of these specimens were less affected by the soaking time. The average shear strength of the CFRP/steel interfaces increased first and then decreased with the soaking time. After soaking for 90 days， the average shear strength of the CFRP/steel interfaces decreased by 35.6% compared with that of unsoaked specimen.