ROS / RNS is a product of normal human metabolism and has important physiological activities. However high concentration of ROS / RNS produces oxidative stress leading to cancer cardiovascular and pulmonary diseases hypertension neurodegeneration diabetes respiratory tract infection rheumatoid arthritis cataract and other oxidative damage diseases. In order to prevent diseases and promote health the sources of ROS/RNS in human body and the relationship between ROS / RNS and diseases were summarized based on a large number of literatures. Common dietary antioxidants such as phenolic compounds vitamin E carotenoids and vitamin C were introduced. The mechanism of scavenging free radicals and antioxidation by different antioxidant compounds was discussed. Phenolic compounds are widely found as antioxidant components of the human diet β-carotenoids are provitamin A and vitamin E are fat-soluble chain-breaking antioxidants that protect the integrity of cell membranes. Vitamin C is water-soluble and its free radical disproportionation rate is much higher than the reaction with other biological molecules such as proteins amino acids DNA etc. Together with the body's antioxidant system they form a reversible antioxidant defense to protect human biomacromolecules from oxidative damage. It is suggested that forming good dietary habits is beneficial to improve the quality of life.