The environment of the tidal zone is very complex. The interactions of dry-wet alternation and sea erosion lead to serious corrosion of steel structures, which makes it difficult to adopt protective methods. Therefore, it is of great significance to study the corrosion and protection methods of steel in tidal zone. For long-scale steel through the tidal zone and immersion zone, there is a big difference in corrosion behavior with complete immersion condition, the potential of the steel surface changes due to the influence of oxygen concentration difference and tidal fluctuations or other factors. In this study, the galvanic current and open circuit potential of the long-scale AH32 steel were monitored in simulated tidal zone. The results shows that the potential at different tide levels and different immersion depths for a long-scale AH32 specimen is not unified, with the macro cell was formed by the difference of oxygen supply, which caused internal galvanic current. The essence of the galvanic current is the net current that was generated by the sum of anode and cathode current. Galvanic current at different positions on the long-scale AH32 specimen varies with the tidal movement periodically in tidal zone. When tide is at the highest level, the galvanic current of all parts accesses a maximum value, and among these maximum values, the largest one is at the middle part of specimen, which causes the biggest anodic dissolution current density. According to the variation of the galvanic current, the time distributions of the drying, wetting and immersion states were calculated, and the results showed that the corrosion scale of the long-scale AH32 specimen at different positions depends on the time all location of wetting and immersion in tidal zone. The macro cell caused the galvanic current when all parts of the specimen were immersed. At wetting state, the solution resistance of the thin liquid film is very large, which leads to the change of the driving potential of the macro cell into the potential drop. Thus, macro cell is ineffective in the wetting state and cannot produce the galvanic current. According to the relation between wetting time and quantity of electricity at wetting state, the maximum wetting time of the long-scale AH32 specimen is shown above average mean tide level in tidal zone, which indicates that the corrosion loss of this part is maximum due to wetting state. In addition to weight loss measurements, maximum of it for long-scale AH32 specimen was obtained at the average mean tide level caused by immersion state. It can be indicated the maximum weight loss of the long-scale AH32 specimen should appear upper the average mean tide level part in tidal zone. These results were consistent with measurements of corrosion rates.