Pyrrhotite is the main sulfide mineral in the Dongguashan ore deposit, one of the most representative stratiform sulfide deposits in the Middle-Lower Yangtze River metallogenic belt. The textures of pyrrhotite in the stratiform ore body indicate that, instead of being magmatic hydrothermal origin, pyrrhotite is the product of desulfurization of the synsedimentary colloform pyrite and pyrite through thermal metamorphism caused by Yanshanian magmatic intrusion. After thermal metamorphism, pyrrhotite was replaced by magmatic hydrothermal fluids.