Abstract: The rule of coloration of 25% ascorbic acid injection of two formulations with different antioxidants under anaerobic degradation was studied at various temperatures (98, 90, 80 and 70℃). At the same time, the rule of coloration of 5% ascorbic acid injection of one formulation was studied at 98℃ for comparison. Experimental re sults indicated that the rule of coloration of ascorbic acid injection may be represented by the following regression equation:where To is the initial transparency of the injection, T is the transparency at time t, T_o′ is the transparency at time to, and t₁ and t₁ are the time when the transparency decreases to about 50% and approaching to 0%, respectively, k is the regression coefficient, which is correlated with the rate of coloration. This equation represents an inverse sigmoid curve. For the upper part of the curve, m is approximately equal to 2, then the regression equation becomesIts approximate equation is:T=T_o-T_okt²=T_o-Kt²The rate equation of coloration of ascorbic acid injection is: The rate of coloration is found to be dependent on the concentration of the injection, the antioxidants and the temperature.