Abstract: The thick oil reservoirs in Chanjiasi are located in loose unconsolidated formation, and oil wells are put into production with wired screen pipe, which is unavailable for zonal steam injection. With the increasing of circulation turns, the zonal inhomogeneity becomes remarkable and such problems as steam channeling and water flooding get more severe. A fluid gelling profile control agent RCY - 1 of 350℃ temperature tolerance is developed, which is suitable of removing steam channeling and water flooding in the thick oil reservoirs; its laboratory test and field using are described. RCY - 1 has a applying temperature range between 200~350℃, gel forming time of 12~2.5h, pressure resistance of higher than 1.33MPa, and can be used for deep plugging. It was used in two wells with remarkable benefits achieved, and a total of 1569 tons of oil was increased.