Abstract: Conventional separate injection operation conducted in Block Yan 50 reservoir were featured by short effective period (only 60 days) and low success rate (33%) due to the high reservoir temperature (has reached to 117 degree). Profile control technique was abandoned because of the poor performance of plugging agent. Based on that, rubber products with temperature resistance and anti-aging additive are used for reference by selecting a heat resistance and anti-aging agent which could improve thermal stability of gels greatly. The process involved in selections in 4 kinds of related additives and experiments of their heat stability. Pilot tests in 2 field wells have illustrated that the temperature resistance agent not only can effectively cope with the heterogeneity in and between layers but also can slow down the speed of water content and output drop, which will enhance the development effect powerfully.