The Huagang Formation sandstone reservoir is an important exploration target in thr Xihu Sag, East China Sea Basin, and the study of reservoir heterogeneity is crucial. Based on the analysis of reservoir diagenesis and diagenetic evolution, this paper clarifies the difference between the north and south of the central inversion zone, and further analyzes the causes of the difference.Methods: In this study, one type of thin sections were made, including casting thin sections and the production process was all in accordance with the Chinese Oil and Gas Industry Standard (Y/T5162- 2014). All the thin sections could be used to analyze the mineral composition and pore geometry. The casting thin sections were stained with blue epoxy resin to identify the pore type and size distribution, and a Leica DM4500P/DFC450C high- precision microscope was used for the observation. SEM is a common electronic imaging technique, which is mainly used to observe the pore structure of rocks at micro/nano scale. This study adopted two methods to observe SEM, one was to use Quanta- 200F field emission SEM (with X- ray energy spectrometer) with a minimum resolution of 1. 2 nm to observe the pore type, mineral composition, diagenesis, and pore connectivity. The XRD experiment could be used to analyze the mineral composition. Before the experiment, samples need to be crushed in an agate container to a particle size of < 200 mesh. Take 100~200 g of the original sample, bake until dry, then weigh it, take an appropriate amount of sediment sample into a container, add water to diffuse, and use a 63~125 μm copper sieve for sorting. After screening out the particle size, it is weighed dry and its mass fraction is calculated; take 1~2 grams of sorted samples, separate them with tribromomethane heavy liquid, dry and weigh them, and calculate the mass fraction of heavy minerals.Results:The northern region has stronger compaction and dissolution, and can be divided into three diagenetic zones, acid, acid—base transition and alkaline, with two stages of siliceous cementation and three stages of calcareous cementation. The southern area has two stages of calcareous cementation with shallow burial depth and low geothermal temperature, and can be divided into two diagenetic zones, acidic and alkaline. The analysis of heavy minerals and hydrocarbon generation intensity shows that the Huagang Formation reservoir in the northern region has the characteristics of low porosity and high permeability.Conclusions: Through thin section observation, scanning electron microscopy, reservoir physical properties, heavy mineral composition, clay mineral content, and other research and analysis, it is believed that the northern region has stronger compaction and dissolution effects. Vertically, it is divided into three diagenetic zones, acid, acid—base transition and alkaline with boundary of 3500 m and 4000 m. It undergoes two stages of siliceous cementation and three stages of calcareous cementation. The southern area, with shallow burial depth and low geothermal temperature, has only two stages of calc cementation, and is divided into two diagenetic zones, acidic and alkaline, with a boundary of 4000 m. Due to the contribution of more magma source rocks, the compressive strength of the Huagang Formation reservoir in the northern region is poor, and it is subjected to stronger compaction, and the stronger hydrocarbon generation strength of source rocks makes the reservoir suffer stronger dissolution. Therefore, the reservoir of the Huagang Formation in the northern region has the characteristics of low porosity and high permeability.