Alkali lignin plugging agent had excellent resistance to temperature and salt，but it had many shortcomings，such as bad toughness，easy to break and short period of validity. In order to improve the toughness of system，the toughening agent was added to conventional alkali lignin plugging agent. The effects of component dosage，including alkali lignin，crosslinking agent and toughening agent，pH value，temperature，salinity and reaction time on the gelling property were studied. The toughness of gel system was evaluated by means of elastic modulus test and infrared characterization. The actual plugging effect was obtained by plugging test with sand filled tube. The results showed that the optimum formula of alkali lignin high temperature gel was obtained as follows：6.0% alkali lignin，5.0% crosslinking agent and 0.5% toughening agent，whose gelation strength was 0.048 MPa and the gelation time was 8 h at 120℃. The gelling pH value of alkali lignin plugging agent system was 7—11，the salt tolerance of that reached to 20 × 10⁴ mg/L，and the temperature resistance of that was 140℃ . The elasticity of gel system was greater than the viscosity，and the elastic modulus of gel increased with increasing concentration of toughening agent. The plugging ability and abrasion resistance of gel plugging agent were good whose plugging rate was above 97%. It could meet the demand of profile control and water shutoff operation in fracture-cavity reservoir with high temperature and high salinity.