Abstract: In order to effectively assess the mechanical properties of concrete exposed to a sea water erosion environment, the degeneration of mechanical properties of concrete cubes was tested after sea water erosion. The concrete stress-strain curve was researched with the number of wet and dry cycles of 0 times, 10 times , 20 times, 30 times, 40 times, 50 times and 60 times based on the large-scale static and dynamic stiffness servo test set. According to the concrete stress-strain curves, the concrete elastic modulus and compressive strength were researched. An erosion tri-axial strength criterion based on OTTOSEN theory was established in accordance with the uniaxial mechanical properties of concrete and damage mechanics. The tests show that the concrete axial compressive strength, modulus of elasticity and other mechanical properties of concrete decline gradually with the increase of the number of wet and dry cycles. The research could be referenced for the anti-crack design of actual structures under a sea water erosion environment.