The amide groups in the polymer （partially hydrolyzed Polyacrylamide and its derivatives） used in chemical combination flooding are liable to be hydrolyzed and their properties changed，resulting in reducing the effect of chemical flooding. A rapid high-performance liquid chromatography method for the determination of the degree of hydrolysis of polymers in trace samples of chemical flooding systems was described. It was used to study the variations of polymer hydrolysis degree in chemical flooding system under different conditions. Experimental results showed that methods could be applied for determination of hydrolysis of polymers in trace sample of chemical flooding，hydrolysis of polymers in the environment of reservoir was affected by connate water，alkali type of chemical combination flooding system，temperature and other factors. The degree of hydrolysis of the polymer prepared with distilled water at 34 ℃ could be obviously detected，oilfield water of NaHCO₃ water-type could promote the hydrolysis of polymers. The rate of hydrolysis reaction in chemical flooding system was in turn：strong base（NaOH）systems ＞weak base（Na₂CO₃）systems ＞ base free systems. The degree of hydrolysis of polymers in various systems increased continuously during the 90 days of experiment when the temperature was above 60 ℃，the degree of hydrolysis of polymers in strong base system was close to 60% after aged for 90 days.