A long history of studying of the antioxidant system enzymes (AOS), lowmolecularweightantioxidants(AO), and reactive oxygen species (ROS) has provided extensive information about their structure, functions, and localization in plant organisms. A large number of currently available studies show how AOS and AO enzymes react to environmental conditions changes; knowledge about the participation of AOS and ROS in the processes of plant life support is actively updated, and how the ROS pool changes qualitatively and quantitatively. In the present review, an attempt was made to show how the AOS system, AO and ROS operate in the implementation of the normal metabolism in plants. The reactions carried out in the processes of growth, development, and aging, as well as signal regulation are considered. The relationship of the AOS, AO, and ROS enzymes with phenolic and carbohydrate metabolism in the plant body is shown.