The Sinian Dengying Formation, a key reservoir in the Sichuan basin, has significant potential for exploration and development. The northern slope of the central Sichuan paleo- uplift has emerged as a frontier area for Sinian- Cambrian natural gas exploration. However, the challenges posed by the substantial burial depth, ancient age, and multi- stage tectonic movements complicate the understanding of reservoir diagenesis. Notably, the reservoir cements within the second Member of the Dengying Formation exhibit a complex diagenetic evolution, so the exploration process of these members is limited to a certain extent. This research investigates the diagenetic history of the second Member of the Dengying Formation in the northern slope of the central Sichuan paleo- uplift by examining petrological characteristics and trace element variations in dolomite cements through thin section identification, cathode luminescence, and in situ micro- region analysis. This study aims to elucidate the diagenetic fluid properties and evolution process, offering insights into reservoir development. Analysis of dolomite cements reveals distinct patterns in trace element distribution, emphasizing the influence of different diagenetic fluids. Fe and Mn content show notable variations across different stages, exhibiting an overall enrichment trend. Conversely, Sr content remains relatively stable, suggesting a general depletion pattern. The first- generation fibrous dolomite and the second- generation bladed dolomite show low Fe and Mn, along with elevated Sr content and high Y/Ho values, indicating a diagenetic fluid derived from normal seawater. The third- generation atmospheric freshwater dolomite displays high Fe and Mn, low Sr, and low Y/Ho values, suggesting an origin in atmospheric freshwater or a mixed fluid environment. From the fourth- generation silty- fine- grained dolomite to the seventh- generation giant crystal dolomite, a gradual increase in Fe and Mn content, elevated HREE abundance, and decreasing Y/Ho values are observed. This suggests that the diagenetic fluid evolved towards formation- sequestered seawater, with the positive Eu anomaly indicating the influence of hydrothermal fluids. The eighth- generation saddle dolomite exhibits high Fe and Mn content and a pronounced positive Eu anomaly, indicating a deep mantle- derived hydrothermal fluid. The findings demonstrate the impact of significant atmospheric freshwater dissolution and burial dissolution in the second Member of the Dengying Formation in the study area. The superposition of organic acids produced by early atmospheric freshwater and late deep hydrothermal fluids, combined with lower hydrocarbons, play a pivotal role in controlling reservoir development within the Dengying Formation on the northern slope of the central Sichuan paleo- uplift.