DNA hydroxymethylation modification is an important part of genome epigenetic regulation.The demethylation process from 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) is catalyzed by Tet protein.Abnormal genomic methylation leads to the occurrence of a variety of tumors.Hydroxymethylation is modified as a kind of demethylation and is inseparable from tumorigenesis.The expression of 5-hmC changes accompanied with the development and progression of digestive system tumors,which may be associated with the TET protein family and IDH mutation.It suggested that DNA hydroxymethylation is involved in the development and progression of digestive system tumors.This paper reviews the relationship between DNA hydroxymethylation and digestive system tumors,and aims to provide a new direction for the study of Hydroxymethylation modification in digestive system tumors.