Abstract: The invention relates to a method of determining amount and/or activity of antioxidants in test samples, wherein a reaction mixture with known initial concentrations of a source of free radicals and a chemiluminescence activator is to measured photometrically starting from the instant of reaction initiation, a reaction rate constant (kR) for generating free radicals and a reaction rate constant (kLum) for eliminating free radicals upon interacting with the activator are calculated based on dependence of light radiation intensity of the mixture on the time of reaction; a new reaction mixture of the above-mentioned source and activator with known initial concentrations and containing antioxidant is prepared; said mixture is measured photometrically; and an initial concentration of antioxidant [In]0 and a reaction rate constant for interaction between free radicals and the antioxidant (kIn) are calculated, based on the change in light radiation intensity in relation to the time of reaction.