Abstract: The 26°S hydrothermal field on South Mid-Atlantic Ridge was found by Chinese scientists,it is the southest hydrothermal field discovered on Mid-Atlantic Ridge. This stydy show that,according to the mineral assemblages , sulfides of chimney from this field, can be classified into three distinct types: Fe-rich,Fe-Cu type and Cu-rich type. The Fe-rich type sulfide is dominated by pyrite-marcasite assemblages ; the Fe-Cu type is dominated by pyrite-chalcopyrite assemblages; and the Cu-rich type si by chalcopyrite-pyrite. Accoding the growth history of a model (ideal) chimney of EPR hydrothermal,chimney from 26°S hydrothermal field is relatively mature.