To address the gas channeling problem in CO2 flooding for low-permeability reservoir development and the easy hydrolysis issue of water shutoff gels under high-temperature and high-salinity conditions, this study prepared a lignin-based double-cross-linked polymer hydrogel (L-PAM-PDEAEMA) resistant to CO2 gas channeling and suitable for high-temperature reservoirs. The preparation used lignin (Lignin), diethylaminoethyl methacrylate (DEAEMA), and acrylamide (AM) as raw materials via cross-linking reaction. Experiments on the CO2 sensitivity, acid resistance, temperature and salt resistance of the hydrogel were conducted using a self-made 200 mL/16 MPa high-temperature and high-pressure reactor (equipped with a gas inlet valve and a pressure gauge). Its mechanical properties were tested by a universal tensile testing machine and a texture analyzer, the reaction mechanism was analyzed by FTIR and XPS, and the structural changes were confirmed by SEM characterization. This study investigated the effect of DEAEMA on the CO2 sensitivity of the hydrogel and the effect of Lignin on its acid resistance, temperature resistance and salt resistance. It was verified that the introduction of DEAEMA and Lignin into the polyacrylamide network can provide a new technical approach for the preparation of hydrogels with both acid resistance and high-temperature and high-salt resistance properties. The research results show that after CO2 treatment under the conditions of 130℃ and 6 MPa, which simulate the actual development environment of oilfields, the compressive strength of the L-PAM-PDEAEMA hydrogel can be significantly enhanced. Meanwhile, it is proved that the hydrogel has excellent temperature resistance and acid resistance. When the addition amounts of Lignin and DEAEMA are 10% and 20% of AM (by mass fraction) respectively, the compressive strength of the CO2-treated L10-PAM-PDEAEMA hydrogel increases from 16 KPa to 151 KPa, with an increase of approximately 8.4 times. FTIR and XPS analyses indicate that the hydrogel forms new ionic cross-linking and hydrogen bonds after CO2 treatment, and the synergistic effect of the two significantly enhances its physical properties. SEM characterization shows that the micro-pores of the hydrogel become denser after treatment, which further confirms its excellent CO2 sensitivity. The hydrogel can still maintain excellent stability after being statically placed for 7 days under the conditions of 130℃, 6 MPa and saline water with a salinity of 21×104 ^mg/L. Tests by a texture analyzer show that its compressive force at 50% strain is 3 N. This study provides a new technical approach for the preparation of hydrogels with combined CO2 sensitivity, acid resistance, temperature resistance and salt resistance, and shows promising application prospects in the control of CO2 gas channeling in low-permeability oilfield reservoirs.