Abstract: Problems such as serious contradiction between layers, water injection adjustment and fingering occurred during waterflooding in the double-step horizontal wells in Hade oilfield. Controlled hydrophobic modification for different carbon chains (C12, C14 and C16) in biopolymers was conducted for 8 biopolymers, and the biopolymers that have the characteristics of thermal thickening and salt thickening, and can be used for high-temperature high-salinity conditions for deep profile modification were composed and selected. The results showed that for the solutions of BP-14-036 and BP-12-012 with the mass fractions of 1.0%, their viscosities were about 10 000 mPa·s; when the salinities increased to 250 g/L, the viscosities exceeded 12 000 mPa·s, indicating the solutions were salt thickening; when the temperature reached 130 ℃, the viscosity of BP-14-036 solution with the mass fractions of 1.0% was over 14 000 mPa穝, indicating the solution was thermal thickening. Therefore, the 2 biopolymer solutions could transfera the extreme conditions of reservoir into the favorable factors to improve profile control effect to a certain extent, which could be used to solve the problems of weak thickening properties and poor tolerabilities of profile control and flooding agent, fracturing fluid and drilling fluid in high-temperature high-salinity oilfields