Water shutoff is the main measure to control water and stabilize oil in Tahe clastic reservoir. However, due to the influence of deep burial, high temperature and high salinity, it is difficult to improve water shutoff efficiency in horizontal wells. In view of this, based on the principle of interpenetrating network polymerization, a composite gel with organic crosslinking agent and silicate as the main body was synthesized. The results show that with the addition of a heat stabilizer, the gelling time of the plugging agent is controllable from 4 hours to 50 hours.The plugging agent does not dehydrate in 30 days at 130 ℃. The water phase plugging rate is over 90%, and it has excellent oil⁃water phase selectivity and formation permeability selectivity. It is necessary to use high⁃efficiency oil wash agent as pre⁃liquid and cross⁃linked polymer as sealing agent to control pressure and inject at low speed during construction. Good application results have been achieved in the field