The conventional blocking agents are hard to solve the problem of steam channeling during steam injection. In order to increase sweep volume and improve oil recovery, the in-depth blocking agents for conformance control are proposed and developed according to temperature gradient in the stratum when injecting steam. The in-depth blocking agents consist of gel system, organic/inorganic cross-linking system and inorganic curing system with different applicable temperature 60~110°C, 120~160°C and 170~300°C. The gel system with temperature resistance is composed of non-ion polyacrylamide and organic cross-linker. The organic/inorganic cross-linking system is composed of organic resin, silicide and stabilizer. The inorganic curing system is composed of superfine cement and stabilizing Na-bentonite. In this paper, the temperature distribution of heterogeneous reservoirs during the process of steam huff and puff is simulated by CMG. According to the above temperature distribution, these blocking agents are separately used for remote zone, transition zone and near wellbore zone of steam injection well. Sandpack flood tests indicate that the in-depth blocking agents have excellent blocking performance. Furthermore, the in-depth blocking agents have been applied to two injection wells in Bin'nan oilfield. After oilfield pilot test, steam injection pressure and daily oil production increased, and the input-output ratio increased to 1:3. The success of oilfield test confirms that the in-depth blocking agents are efficient to control steam channeling.