Abstract: Authigenic microcrystalline quartz coating and quartz secondary overgrowth are the most important authigenic minerals in the Jurassic sandstones of the Qikou sag, Bohai Bay basin. Primary pores related to microcrystalline quartz are well developed in the reservoir with deep burial depth. Based on the analysis of thin section, SEM, cathode luminescence, electronic probe and X-ray diffraction, the paper studies the source, growth pattern and formation mechanism of microcrystalline quartz coating, protection of primary intergranular pores and inhibitory mechanism of quartz secondary overgrowth in the study area, and verifies the diagenetic evolution sequence of the authigenic microcrystalline quartz coating sandstone. The microcrystalline quartz formed in early time, grew parallel to host grains and could rotate arbitrarily along the C axis. The associated primary pores are well developed. The analysis of the genesis of the authigenic microcrystalline quartz coating and its diagenetic evolution sequence is of great significance for the research on forming mechanisms of high-quality deep and ultra-deep reservoirs and petroleum exploration and development in Bohai Bay basin