Overpressure strongly influences gas migration and trapping in deep high-temperature/high-pressure (HTHP) reservoirs. However, its time-dependent evolution is commonly poorly constrained by direct, quantitative pressure proxies. Here we combine quantitative Raman spectroscopy and microthermometry of fluid inclusions with 1-D burial–thermal modelling to reconstruct multi-stage pore-pressure evolution associated with CH4-CO2 charging in Upper Miocene Huangliu Formation sandstones on the Ledong Slope, Yinggehai Basin. Fluid-inclusion petrography was used to target gas-rich inclusions and petrographically associated aqueous inclusions hosted by quartz microfractures and quartz overgrowths. Raman analyses quantify CH4-CO2 compositions and gas densities using the CO2 Fermi diad splitting and the position of the CO2 v1 band, while dissolved CH4 in aqueous inclusions is quantified using calibrated Raman peak-area methods. Trapping pressures are calculated by integrating Raman-derived densities/compositions with homogenization temperatures of coeval aqueous inclusions and appropriate equations of state; CH4-CO2 mixed-gas inclusions provide an internal consistency check (pressure deviations ≤1.7 MPa). CO2-rich inclusions define three reproducible density populations that correspond to three pressure stages from near-hydrostatic to strong overpressure (~27–47, ~58–74, and ~87–107 MPa). Mapping trapping temperatures onto burial histories indicates three CO2 charge episodes (2.0–1.8 Ma, 1.8–1.6 Ma, and ~1.2 Ma) and two CH4 episodes (~1.5 Ma and ~0.4 Ma). Peak palaeo-pressures approached ∼98% of lithostatic stress, implying that late high-pressure CO2 charging can locally exceed fracture thresholds, generate microfractures, and enhance gas migration and accumulation, while overpressure can be preserved over geological timescales. The reconstructed pressure history is consistent with present measured reservoir pressures, demonstrating that multi-phase quantitative Raman inclusion barometry (CH4, CO2, mixed CH4-CO2, and dissolved gas in aqueous inclusions) provides robust constraints on pressure evolution and pressure-controlled gas enrichment in overpressured basins.