Abstract: Aiming at the needs of stronger heterogeneity, high salinity and low oil price for offshore oilfields, this paper uses experimental measurements and mechanism analyses to study the preparation, gelling characteristics, and plugging effects of inorganic gel system (IGS). The results show that when the liquid sodium silicate is between 0.4% and 3%, after being injected into the Bohai formation, the agent reacts with Ca²⁺ and Mg²⁺ in the formation water, and forms inorganic silicate gel with a density approximating to formation water. The agent is a kind of liquid system, which the strength is controllable and can be injected online. The new agent features fast solution, temperature resistance, salt resistance, environmental friendly, and cost-effective. When low concentrations of liquid polymer (500 mg/L) and chelating agents (0.1%) are added, a more strengthened inorganic composite gel system is obtained and it can further improve the viscosity and strength of system. Results of the core flooding experiment show that IGS+ emulsion polymer system can significantly improve the flow resistance. The plugging efficiency is between 24.73%~70.38%, showing a good deep profile control ability. This study might be practical to apply the new agent in high salinity offshore oilfield.