Lenghu uranium deposit is a newly discovered in recent years and have industrial value sandstone-type uranium deposit in the northern part of the Qaidam Basin. In order to study the classification, occurrence and mineralization of uranium minerals in this area,this paper conducted the mineralogical, electron probe, backscatter electron imaging analysis of the altered minerals in Xiaomeigou Formation of Lower Jurassic on the basis of field investigation. These studies found that the ore types of Xiaomeigou Formation in Lenghu are mainly composed of complex sandstone-type and carbonaceous sandstone-type, which have occurred overall epigenetic alteration. It is found that the main uranium minerals are uranite, pitchblende and minor of lead selenite, which is closely associated with clay minerals, organic matter, and pyrite, and lie in the intergranular space of quartz, feldspar and other altered lithic mineral grains or in cleavage joints of altered minerals occurs in fine columnar, gel-like or irregular sawtooth shape. In late multiple fluid processes, U⁶⁺ occurred reduction-precipitation-adsorption uranium mineralization in the reduction environment provided by Fe²⁺. Based on the analysis of high Y and low Y-types uranium minerals, alteration sequence and environmental characteristics, it is inferred that uranium in uranium minerals was the residual of original uranium minerals, which is enriched and mineralized by multi-stage transformation of fluids with no Y element or very low Y element.