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In view of the current situation that constructing an occluded cell model can only enable the study of localized corrosion of stainless steel in single halogen-containing system, a new occluded cell model for studying the development of localized corrosion of 304 stainless steel in a fluorine-chloride ion coexistence system was constructed, and the working conditions and main influencing parameters of such model were determined through single factor tests and orthogonal tests respectively. Meanwhile, the usability of the model was verified taking into account the pH value of the occluded zone, ion migration, corrosion current and corrosion rate. Results showed that for the constructed occluded cell model for the study of localized corrosion development of 304 stainless steel in the flue gas ammonia desulfurization slurry, an applied voltage of 0.8 V and a solution temperature of 50 ℃ were good working conditions. The optimal combination of influencing parameters was as follows: a ratio of internal solution volume to anode exposure area of 59, a ratio of cathode exposure area to anode exposure area of 10, and a simulated rust thickness of 3 mm. Moreover, the model presented good usability in media containing different concentrations of fluorine ions and chloride ions.