Polymer gel has been widely used in high water cut reservoirs for enhanced oil recovery (EOR), while its effectiveness is often curtailed in ultra-high temperature reservoirs for the indeterminate stability. In the present work, the ultra-high temperature resistant gel was constructed with P(AM/NVP) as the main agent, hydroquinone and Polyethylenimine (PEI) as the crosslinking agent, and the EOR potential of P(AM/NVP) based gel is studied at 150 °C, including injectivity, plugging property, and oil increasing performance. The experimental results indicated that the base solution of P(AM/NVP) based gel could establish resistance factor of 17.5–182.5, the plugging rate of the gel exceeded 96%, and the breakthrough pressure gradient ranged from 17.99 MPa/m to 46.54 MPa/m in matrix cores. For fractured cores, the plugging ratio surpassed 95%, and the breakthrough pressure gradient decreased to 9.56 MPa/m ∼24.32 MPa/m. Moreover, within a permeability ratio of 5.90–28.75, the water cut could be decreased from 98.0%–100.0%–50.9%–65.81%, with an increase in oil recovery of 20.10%–44.30%. In addition, NMR experiment verified the gel blocking channeling channel and expand the sweeping efficiency of chase water flooding. This study's findings showed that P(AM/NVP) based gel has excellent EOR potential in ultra-high temperature reservoirs.