The aim of this work has been to find a simple, non-destructive method for determination of the concentration of active antioxidant in HTPB/AP composite propellants. Differential Scanning Calorimetry (DSC) was used for determination of Oxidation Induction Time (isothermal OIT) and Oxidation Induction Temperature (dynamic OIT) at different antioxidant concentrations. The ammonium perchlorate content in the propellants were 80% by weight. The antioxidant was BKF with concentration up to 2.5% by weight of the polymer. Iron oxide was added to some of the samples, and to one of these samples aluminium was also added. The results show that the dynamic OIT depends on the active antioxidant concentration, and useful calibration curves were obtained for the propellants with and without iron oxide. Concentrations of active BKF up to 1.5% by weight of polymer could be determined using this method. Aluminium content in the propellant had no effect on the results. The results also indicate that the isothermal OIT cannot be used for determination of the active antioxidant concentration.