Abstract: The northern Da Hinggan Mountains area is one of the most important polymetallic metallogenic belts, where the Kulundi-Najihe lead-zinc-silver deposit was discovered in recent years. Recent exploration shows medium to large scale reserves of lead and zinc resources and large scale silver resources. This paper mainly presents the researches on orebody characteristics and analytical results of fluid inclusions and stable isotopes in order to better understand the origin, metallogenic age and tectonic setting of the Kulundi-Najihe lead-zinc-silver deposit and further to make the exploration breakthrough of the lead-zinc-silver-polymetallic deposits in north Da Hinggan Mountains. The analytical results show that fluid inclusions in the deposit mostly belong to typical gas-liquid inclusions, with the metallogenic temperature ranging from 310 to 340℃, the salinity of the ore-forming fluid lower than 6%, and the density being 0.67~0.70g/cm3, suggesting that the ore-forming fluid was probably derived mainly from the post-magmatic hydrothermal solution, with the addition of some surface water. Isotope analyses of S, Pb indicate that the ore-forming material was mostly derived from the depth with characteristics of mantle source, and the crust-mantle mixing post-magmatic hydrothermal fluid probably extracted ore-forming materials from old strata. The model age of Pb isotope single-stage evolution curve was used to constrain the metallogenic age, and the results obtained show that this deposit was formed in two periods, i.e., about 175Ma and 138Ma respectively. It is held that the deposit belongs to a typical epithermal deposit related to post intermediate-acidic magmatism.