Abstract: In recent years, significant progress has been made in deep to ultra-deep shale gas exploration of Wufeng-Longmaxi formations in southeastern Sichuan Basin. This formation generally exhibits overpressure and high gas content, but formation pressure and gas content show significant differences in different structural areas, with some areas exhibiting normal pressure and low gas content characteristics. Overpressure is not only a key factor for high shale gas production, but also an important indicator for evaluating preservation conditions. However, its genesis mechanisms and preservation mechanisms remain unclear, constraining the effective exploration and development of shale gas in this area. Taking the Dingshan-Dongxi area in southeastern Sichuan Basin as an example, through logging data analysis and fluid inclusion measurement, deep shale overpressure genesis and its preservation mechanisms were systematically investigated. The logging combination analysis demonstrated that the corrected acoustic time (AC) curve in overpressure intervals significantly deviated from the normal compaction trend, while the density (DEN) curve remained generally stable or slightly decreased. Both the acoustic velocity-density crossplot method and the Bowers method indicated that normal pressure data points were distributed near the loading curves, while overpressure data points mainly fell along unloading curves. Additionally, based on pressure restoration of methane inclusions in shale fracture veins of Wufeng-Longmaxi formations, the average trapping pressure of 83-142 MPa was obtained, corresponding to a formation pressure coefficient of1.56-2.06. These two methods collectively confirmed that hydrocarbon generation was the main controlling factor for shale overpressure formation in this area. Overpressure preservation was controlled by good hydrocarbon source foundation, strong sealing roof-floor conditions, and relatively weak tectonic activity during tectonic uplift. The research findings clarify the genesis and preservation mechanisms of deep shale overpressure, providing a basis for the further exploration and development of shale gas in southeastern Sichuan Basin.