The corrosion degradation behavior of concrete materials plays a crucial role in the change of its mechanical properties under multi-ion interaction in the marine environment. In this study, the variation in the macro-physical and mechanical properties of concrete with corrosion time is investigated, and the source of micro-corrosion products under different salt solutions in seawater are analyzed. Regardless of the continuous hydration effect of concrete, the damage effects of various corrosive ions (Cl^–, {\mathrm{S}\mathrm{O}}_4^{2-}, and Mg²⁺, etc.) on the tensile and compressive strength of concrete are discussed based on measurement in different salt solutions. The sensitivity analysis method for concrete strength is used to quantitatively analyze the sensitivity of concrete strength to the effects of each ion in a multi-salt solution without considering the influence of continued hydration. The quantitative results indicate that the addition of Cl^– can weaken the corrosion effect of {\mathrm{S}\mathrm{O}}_4^{2-} by about 20%, while the addition of Mg²⁺ or Mg²⁺ and Cl^– can strengthen it by 10%–20% during a 600-d corrosion process.