In order to explore the corrosion characteristics of steel bars in cracked concrete under carbonation， the carbonation law of hardened cement pastes with cracks under carbonation was studied by controlling crack parameters， and the corrosion area rate， weight loss rate and electrochemical corrosion parameter characteristics of steel bars in hardened cement pastes with cracks were clarified. The results show that the crack width of the hardened cement paste with cracks in the early stage of curing has a more significant effect on the corrosion of steel bars than the water-cement ratio， and the influence of the crack width on the corrosion of steel bars gradually increases and plays a dominant role in the later stage of curing. There are two capacitive arcs in the Nyquist diagram of a cracked hardened cement paste under carbonization. As the age of carbonization increases， the capacitive arc resistance in the low-frequency region gradually shrinks， the transfer resistance of the electric double layer on the surface of the steel bar decreases， and the steel bar begins to remove the passivate film. Within a certain range of crack width， when the water-cement ratio is small， the corrosion of steel bars in hardened cement pastes can be suppressed.