In order to investigate the effects of Spartina alterniflora invasion on the variations of inorganic sulfur fractions and its main influencing factors in soils, the marshes with different invasion years of S. alterniflora (SA1:5-6 a; SA2:8-10 a; and SA3:12-14 a) in Shanyutan of the Min River estuary were studied by the method of space-for-time substitution. Results indicated that the contents of water-soluble-sulfur (H₂O-S) in soils generally increased with increasing invasion years, while those of adsorbed-sulfur (Adsorbed-S), HCl-soluble-sulfur (HCl-Soluble-S) and HCl-volatile-sulfur (HCl-Volatile-S) generally decreased. Compared with SA1, the levels of H₂O-S in soils of SA2 and SA3 increased by 10.02% and 2.68%, whereas those of Adsorbed-S, HCl-Soluble-S and HCl-Volatile-S decreased by 9.02%, 10.95%, 7.57% (SA2) and 15.61%, 32.89%, 15.14% (SA3), respectively. The total inorganic sulfur (TIS) contents, TIS stocks and their proportions in total sulfur (TS) stocks in marshes decreased with the increasing invasion years, and the decline mainly rested with the contributions of Adsorbed-S, HCl-Soluble-S and HCl-Volatile-S. Moreover, with increasing invasion years, the environmental factors affecting the fractions of inorganic sulfur changed greatly. Thereinto, the alterations of soil grain composition, electrical conductivity (EC) and pH showed great effects on the variations of inorganic sulfur fractions. This study found that, with the increase of invasion years and the implementation of regular mowing activities for S. alterniflora, the inorganic sulfur nutrient in marshes would decline and become deficient, which might weaken the invasion capacity of S. alterniflora in the long term.