Abstract: Circulating tumor DNA (ctDNA) is a tumor-derived fragmented DNA in blood and is a characteristic marker of tumor. Through the correlative detection of ctDNA, the trace information of the tumor in the blood of the patients can be detected, and the panoramic data of the tumor can be provided. As a non-invasive detection method, ctDNA plays an important role in the screening, prognosis and treatment of tumors. This article will describe the origin of ctDNA, the detection technology of ctDNA, the potential application of ctDNA in tumor detection and treatment, and the related problems faced by ctDNA detection technology.