Down syndrome as the most common chromosome abnormality, and the most common cause of mental retardation in human societies, is responsible for over one-third of learning disorders. Children with Down syndrome are usually smaller in size compared to other children, and their mental and physical development stages are slower than their peers. This syndrome has different symptoms including major or minor abnormalities in the structure or function of body’s organs. Incidence of some disorders that can be serious health threats, such as oxidative stress, cancer and obesity in patients with Down syndrome are more common than other people in community. This paper meanwhile describes the mechanisms of incidence of these complications, also refers to some points about prevention and reduction of their pathogenesis.