In order to plug the gas channeling passage in the fractured reservoir，a modified cellulose gel used as plugging channeling agent at the high-pressure CO₂ environment，composed of 2% modified cellulose + 2% acrylamide + 0.1% crosslinking agent（N，N'-methylenediacrylamide）+ 0.03% ～ 0.1% initiator，was developed，and the viscoelasticity，thermal stability and plugging performance of the gel was investigated by bottle test，SEM，and rheological test，respectively. The results showed that under the high-pressure CO₂ environment of 10 MPa，the gelling time was controlled from 6 to 24 h，the viscosity of the gel could achieve 18×10⁴ mPa·s，and the elastic modulus and loss modulus of the gel was 3500 Pa and 500 Pa at 1 Hz，respectively. The gel could be stable under the high pressure gas environment for a long time. After placed for 120 d，the performance of the gel was relatively weakened due to the effect of acidification and gas penetration，the microstructure became relatively sparse，however，it still had the nature of the semisolid and the elastic modulus and the loss modulus was 2100 Pa and 280 Pa at 1 Hz，respectively.After plugging，the gas flow rate decreased from 23000 mL/min to 830 mL/min，which was close to the homogeneous core gas velocity（640 mL/min）. The cellulose gel could be used to plug the gas channeling under high pressure CO2 environment in the fractured reservoirs.