In order to study the corrosion behavior of pre-rusted rebars in marine concrete environment, the corrosion behavior of two kinds of rebars in concrete pore simulating solution containing 3.5wt.% NaCl was investigated by electrochemical test methods such as open circuit potential, electrochemical impedance spectroscopy, and kinetic potential polarization curves using the reinforcing bars with 3-months natural exposure as the research object and the unexposed rebar as the control, and the surface physical phases of the reinforcing bars were analyzed by XRD and Raman spectra, the micro-morphology of the reinforcing bars was characterized by SEM. The results showed that the corrosion tendency of the two types of rebars gradually increased and the corrosion resistance gradually decreased under the continuous erosion of chloride ions. The total resistance Rt values of rusty and normal rebars were 14.7 kΩ·cm2 and 35.5 kΩ·cm2 after 1 h of immersion, respectively, and decreased to 2.3 kΩ·cm2 and 5.5 kΩ·cm2 after 10 d of immersion. The breakdown potentials and passivation current densities of rusted and normal rebars were −354 mV, −375 mV and 0.264 mA/cm2, 0.154 mA/cm2, respectively, after immersion for 10 d. Combined with the analytical results, it can be seen that the surface of the steel bars is loose and porous due to γ-FeOOH produced by the natural exposure, which is a poorer barrier to the chloride ion erosion, and it is more likely to cause the aggregation of chloride ions, and This leads to the deterioration of corrosion resistance.