The Lu Zong Mesozoic volcanic Basin is located in the lower Yangtze River fault depression zone, where is the north margin of the Yangtze Block. There are many magnetite apitite deposits called Porphyrite iron deposits by the Chinese scientists. Nihe iron deposit located in the northwest part of Lu Zong basin, it is a newly found large iron sulfur anhydrite deposit. Anhydrite is widely developed in almost each alteration mineralization stage of Nihe deposit. Deep exploration work has revealed gypsum bearing sedimentary rock deeper than 1800M below under the surface in the basement strata of Lu Zong basin. However, the relationship between gypsum salt layer and mineralization has not attracted much attention. Based on geology and geochemistry characteristics of Nihe iron deposit, the evolution process of ore forming fluid system, the metallogenic mechanism and the characteristics of gypsum salt layer have been discussed in this paper. The huge amount of anhydrite in iron ore bodies and altered wall rocks were mostly came from the underlying gypsum salt layer indicated by sulfur isotope (δ34S) and strontium isotope (87Sr/86Sr)i constrains. Geological and geochemical studies all show that Triassic gypsum salt layer has played an important role in the formation of Nihe iron deposit. The gypsum salt layer provided plenty of sulfur and mineralizing agent. Gypsum salt layer is weak positions mechanically, which is prone to collapse and interlayer sliding between the layers when upward migration of magmatic hydrothermal invading and contacting with the gypsum salt layer, this can provide channels for magmatic and hydrothermal emplacement and migration. On the basis of the above analysis, A two stages of metallogenic model for Nihe deposits has been set up: the gypsum and salt sedimentation period in the middle late Triassic (probationary period) and the magmatic hydrothermal mineralization period in early Cretaceous.