DNA methylation is one of the most widely used indicator for early cancer screening. Under the influence of carcinogens, hypermethylation of the promoter region of tumor suppressor genes may lead to downregulation or silencing of gene expression, thereby activating the expression of proto-oncogenes and promoting tumorigenesis. The samples used for DNA methylation detection are mainly exfoliated cells, blood samples and paraffin-embedded tissues. Commonly used detection methods include: methylation-specific polymerase chain reaction (MSP), nucleic acid mass spectrometry, methylation chip, bisulfite sequencing, next-generation sequencing, etc. Compared with mutation detection, the advantages of DNA methylation detection are that it has higher tumor specificity, more detectable sites, higher signal quality, and can achieve tissue traceability. Currently, it is mainly used clinically for medication guidance for brain glioma, aid in diagnosis and high-risk triage for lung cancer, high-risk triage and recurrence monitoring for bladder cancer, high-risk triage for cervical cancer, and early screening and recurrence monitoring for colorectal cancer and gastric cancer. Before large-scale clinical routine application, accurately positioning of the application scenarios for DNA methylation detection must be considered. For well-tolerated endoscopy, the rigid need of DNA methylation detection for high-risk triage may be reduced. DNA methylation detection plays an important role in assisting in the diagnosis of tumors with low pathological diagnosis sensitivity, tumor monitoring and prognosis assessment. With the standardization of testing procedures and quality management, DNA methylation detection will be more widely used to improve the early screening and diagnostic sensitivity of tumors.