Abstract: Sewers in coastal cities are suffering from pipeline breakage and seawater intrusion caused by tide. The periodically entered sulfate-laden seawater significantly changed the sulfate level and hydraulic retention time in tidal sewers. As a result, odor and pipe corrosion problems occur due to the hydrogen sulfide formation. In order to evaluate the influences on sulfide formation in tidal sewer sections by tide, experiments were conducted to simulate sulfide formation in a tidal sewer section. The results showed that the seawater intrusion by tide significantly increased the peak sulfide concentrations in the sewage and resulted in serious sulfide pollution. The sulfide peaks appeared at the lowest tide every day. However, aerobic seawater to some extent oxidized and diluted the sulfide produced in the tidal sewer section, alleviating the serious sulfide problem. The developed mathematical model well simulated the tidal sewer processes, especially the sulfide transformation. Using this model, nitrate dosing as a sulfide control measure was evaluated and optimized for this modeled tidal sewer section. The results reveal that, tide would seriously promoted the sulfide formation and increased peak sulfide concentration in tidal sewer section, and the proposed tidal sewer process model would be a helpful tool for further research and sulfide control.