The data of the research of age features of oxidation system in dogs are given in the article. As a result, standards on content of lipid peroxidation products in blood in dogs of different age, as well as concentration of antioxidants and activity of enzyme antioxidants have been detected. These data give the assumption that the intensive aging starts from the age of 7 in dogs of large breeds, which indicates to possible correction of age-related changes in this very age.