Longwan deposit is located in the central Guizhou-northwestern Hunan uranium mineralization belt. It is the first discovered large-scale uranium deposit in Guizhou Province in recent years. Taking Longwan deposit as the research object, this study has focused on its mineralogy, geochemistry and genesis. The result shows that the primary uranium mineral in this ore consists mainly of pitchblende, while the secondary uranium ores formed under surface conditions are well developed, mainly including silicon calcium uranium, selenium, lead, titanium, uranium and urinal phosphate mineral, etc., with nanometer-micro level of granular ( particle size of <10,m), stringer, or implicit crystalline forms occurring in in the uranium minerals ( organic matter, clay minerals, etc.). The ore-forming materials mainly come from ore-bearing horizon, and some may come from basement magmatic rocks. The ore-forming fluid is the mixture of deep fluid and meteoric precipitation. The enrichment of uranium and associated elements is closely related to carbonaceous mudstone with abundance of organic matter, phosphate mineral, iron ore and clay minerals. The formation of uranium ore is controlled by such factors as stratum ( Laobao Formation), lithology ( carbonaceous mudstones), structure (fault of Sansui syncline and oblique tangential syncline, interlayer fault), sedimentary environment ( marine reductive sedimentary environment of continental rifts and rifts). It experienced the mineralization process of uranium enrichment during the formation of ore-bearing rock series under the action of seafloor jets in Xuefeng period, followed by leaching, hydrothermal superposition and re-enrichment under the background of intraplate extensional tectonic movement in Yanshan-Himalaya period, is described. Epigenetic metallogenic characteristics are obvious, and the deposit belongs to sedimentary-hydrothermal superposition transformation type. The research results of this paper have important guiding role and reference significance for promoting uranium mineralization prediction and prospecting exploration and enriching carbonaceous and siliceous mudstone uranium mineralization theory in eastern Guizhou.