Abstract: As a heritable regulation,epigenetics can regulate gene expression by other ways without changing the DNA sequence,and change cell or individual phenotypes.DNA methylation is an issue in the field of epigenetics research.Recently,many studies have been demonstrated that the methylation of repetitive DNA,specific gene and CpG island and loss of imprinting play an important role in tumor occurrence.As the development of technological approaches to DNA methylation,we have a more comprehensive understanding on methylation patterns.As specific markers,abnormal methylation sites in the genome can be used in the diagnosis,treatment and prognosis predictor of disease.For tumor development caused by DNA methylation,the application of demethylating drugs have achieved good effect in clinical treatment.