As a non-or minimally invasive examination method, liquid biopsy can be used to analyze and detect genetic information of tumors in body fluids, which has broad application prospects. In central nervous system tumors, the content of circulating tumor DNA (ctDNA) in cerebrospinal fluid is higher, which can better demonstrate the characteristics of tumors. At the same time, with the continuous development of analytical techniques, such as digital polymerase chain reaction and next-generation sequencing technology, liquid biopsy based on cerebrospinal fluid has developed faster. This review focuses on the clinical application of cerebrospinal fluid ctDNA in central nervous system tumors and emphasizes on the role of ctDNA in diagnosing tumor, guiding tumor precise treatment, evaluating treatment effects, and preventing relapse, etc. Besides, several detection techniques for liquid biopsy are briefly introduced at the end of this review.

Liquid biopsy; Cerebrospinal fluid; Circulating tumor DNA; Central nervous system; Neoplasms