To investigate the distribution and major influencing factors of the inorganic sulfur forms on Phragmites australis marsh (PA), Cyperus malaccensis marsh (CM), and ecotonal marsh (P. australis-C. malaccensis marsh; PCM) in the Shanyutan tidal wetlands of the Min River Estuary. Results showed that during the spatial expansion between PA and CM, the contents of H₂O-sulfur, adsorbed-sulfur, and HCl-soluble-sulfur in the soils of PCM (0-40 cm) were generally higher than those of PA and CM; however, the values of HCl-volatile-sulfur was just in the opposite. In the vertical direction, the contents of H₂O-S, adsorbed-S, and HCl-soluble-S in different marsh soils decreased initially, followed by a subsequent increase, while the values of HCl-volatile-S was just in the opposite. The average of the different inorganic sulfur forms generally followed the order of HCl-soluble-S > H₂O-S > adsorbed-S > HCl-volatile-S. The average total inorganic sulfur (TIS) content accounted for 22.29%-39.99%, 32.39%-33.33%, and 30.20%-30.86% of the average total sulfur (TS) content in the soils of the three PA, PCM, and CM, respectively. Compared to PA and CM, the contents of H₂O-S, adsorbed-S, HCl-soluble-S, and TIS in the soils of PCM increased by 36.94% and 54.31%; 34.84% and 13.03%; 73.25% and 67.59%; and 45.72% and 45.28%, respectively, while the levels of HCl-volatile-S decreased by 2.78% and 22.24%. The contents of H₂O-S, adsorbed-S, and TIS in different marsh soils were mainly controlled by the organic matter and particle composition, whereas the values of HCl-soluble-S and HCl-volatile-S were dependent on the oxidation-reduction environments and the distribution of metals. This study found that the spatial expansion of the two plants not only improved the supply capacity of the available sulfur in soils but also reduced the adverse effects of volatile sulfide on the growth of the two plants, which was of great significance in maintaining their strong competitiveness in PCM.