Abstract: High-temperature sandstone oil reservoirs with stronger heterogeneity that have been developed by means of water flooding for a long period suffer several development problems, such as fast rise of water cut, complex distribution of remaining oil and high difficulty of conventional treatment. And generally in-depth flooding control technology can be used to improve their development effects. The reservoir in Fault Block L of Huabei Oilfield has the temperature as high as 115 ℃, and it is in the late development stage with high water cut and high degree of reserves recovery. As for this reservoir, numerical simulation method is applied to macroscopically investigate remaining oil distribution and determine dominant water channels, a new type of high-temperature cross-linking agent is developed independently, and multi-well group synchronous flooding control mode is adopted in the field test. 44 150 m³ flooding control agent is totally injected into five well groups. The daily oil increment in the peak period is 25 t and the composite water cut drops by 9.5 %. The cumulative oil increment by December 2019 is 12 780 t. The field test results show that the study on remaining oil distribution and the determination of dominant water channels provide the reliable basis for the design of flooding control scheme and the movable gel system with high-temperature composite cross-linking agent presents remarkable effect of water production decrease and oil production increase when it is applied to flooding control in Fault Block L. The research results provide successful technical reference for the in-depth flooding control of similar oil reservoirs.