The hydrothermal type lead and zinc deposit in northeast Yunnan It has certain mineral assemblage zoning characteristics, the research is lower in this area,this paper for the example of the Maozu lead and zinc deposit of in the northeast of Yunnan province,we use of Eh—pH phase diagram research the balance conditions and change trends of various kinds of metallogenic substances among, from this point of thermal equilibrium condition of Eh—pH, probes the mechanism and characteristic of certain mineral assemblage zoning characteristics of hydrothermal type lead and zinc deposit in northeast yunnan,enriching and improving the physical chemical condition this type of ore deposits origin through this research for the mechanism of metallogenic fluid evolution and mineralization it provides some theoretical basis. Methods:Through field investigation and indoor research, think the northeast hydrothermal type Pb—Zn deposit metallogenic process belongs to the typical solid—liquid phase reactions in mineral balance of thermodynamics, built within the stability of the water balance equation of mineral assemblage of the deposit, using research mineral thermodynamic equilibrium and thermodynamic data calculation and drawing Eh—pH phase diagram of Maozu Pb—Zn deposit Fe—S—Pb—Zn—H—O system,to discuss this Eh—pH among physical chemical condition of oreforming fluid. Results:Through the phase diagram show that mineral assemblage zoning characteristics,be due to pH and Eh dual control,when the Eh value is above 0.5V the metallogenic elements exist in the form of ions or sulfates, when the Eh value below 0.5V the sulfide happen reduction and precipitation. as the pH increases, the metallogenic elements shift in the form of sulfates removal, from the diagram the range of stability of Pyrite, lead ore all contains the range of stability of sphalerite the stability of the sphalerite is significantly broad than the between, it shows that when the precipitation of pyrite and lead ore is precipitated in different time and space, the sphalerite can continue to move and deposit. on the other hand, this phenomenon explains the macrogeological characteristics of the hydrothermal type lead—zinc deposit in the northeast of yunnan province with lead, zinc, iron symbiosis and zinc as the main proportion Conclusions:The method of Eh—pH phase diagram has been successfully applied to the hydrothermal type lead and zinc deposit in northeast yunnan restriction physical chemical condition of metallogenic migration and precipitation the metallic mineral assemblage characteristics of ore deposit are controlled by Eh and pH, the phase diagram reflect the zoning pattern to with the geological characteristics of the ore deposit are matched.