The Triassic Baikouquan Formation in the the Junggar Basin has huge oil and gas exploration potential, but the reservoir sand body has poor physical properties and strong heterogeneity. The reason for the formation of high-quality reservoirs is not yet clear, and the understanding of diagenetic characteristics is vague, which limits the exploration and development of oil and gas in this area. Based on the core observation,thin section analysis, scanning electron microscopy and physical property analysis, the diagenesis and pore evolution of the reservoir from the Baikouquan Formation are analyzed in detail. The results indicate that the rock type of the Baikouquan Formation in the study area is mainly sandy conglomerate, and the reservoir can be divided into reservoir supported by sand and gravel and supported only by sand. The overall reservoir space is mainly composed of primary intergranular pores with poor physical property, belonging to the low porosity and low permeability type. The diagenetic stage of the reservoir is the middle diagenetic stage B. Based on quantitative analysis, it was found that compaction and cementation have a significant impact on the physical properties of the reservoir. The pore increasing ability of dissolution is controlled by the type of rock support, and has a significant impact on the pore increasing of reservoir rocks supported by sand and gravel, while it has a relatively poor impact on the pore increasing of reservoir rocks supported by sandy particles.