Down' s syndrome results form abnormal meiosis of 21 chromosome and has many kinds of abnormal phenotypes,for example,cognitive impairment,learning disability,mental retardation,congenital heart defect,early onset of Alzeimer' s disease and leukaemia.There are different each phenotypes among Down' s syndrome individuals.That is,not each individual will have all kinds of these abnormal phenotypes,moreover,the severe degree of each phenotype is also various,which may be related to the environment and genetic factors.Therefore,It is important to identify the correlation between genes and phenotyes,which has very important significance for susceptibility gene locating and gene therapy.This article will review the progress in the correlation between genes and phenotypes in patients and animal models with Down' s syndrome.