Abstract: The second member of the Xujiahe Formation in the Hexingchang area of western Sichuan features tight sandstone reservoirs characterized by "ultra-low porosity and ultra-low permeability, " with an average matrix porosity of 3.4%–3.7% and an average matrix permeability of 0.07–0.08 mD. To clarify the electrical response characteristics of this reservoir during nitrogen flooding, this study conducted experiments using a high-temperature and high-pressure core flooding system with synchronous resistivity and polarization measurements. Under conditions of 120°C, 100°C, 74 MPa, and 60 MPa, nitrogen was injected at a constant flow rate of 1 mL/min, and real-time data on core resistivity and polarization during the flooding process were collected. By analyzing the influence of temperature, confining pressure, and porosity on resistivity and polarization responses, the main factors controlling the electrical property changes of the reservoir were elucidated. The results indicate: (1) Rock resistivity and polarization generally exhibit a four-stage evolution pattern during flooding—"initial slow increase—mid-stage sharp rise—subsequent gradual rise—final stabilization"; (2) Elevated temperature significantly enhances flooding efficiency, reduces residual water saturation, and markedly increases resistivity growth; (3) Pressure has relatively weaker effects on electrical parameters, primarily influencing polarization responses through water saturation regulation and coupling with temperature; (4) The better the reservoir physical properties, the more pronounced the resistivity and polarization responses to temperature and pressure changes, particularly highlighting polarization characteristics in medium and higher-quality reservoirs under low-temperature conditions; (5) Nitrogen flooding primarily affects rock electrical properties by altering water saturation, with the mechanism attributed to conductivity network reconstruction induced by saturation changes. This study provides experimental evidence for electrical interpretation and fluid identification in tight sandstone reservoirs under high-temperature and high-pressure conditions, while emphasizing the need to consider dynamic changes in electrical parameters during the flooding process in practical electrical method applications.