Abstract: Central nervous system (CNS) malignancies are difficult to diagnose in early stage, with the characteristics of insensitive to traditional therapy and easy to recur, resulting in poor prognosis. Early diagnosis and treatment response monitoring are challenging because of high risks of stereotactic biopsy in deep brain regions, and low specificity and sensitivity of the circulating tumor cell DNA (ctDNA) using peripheral blood. Therefore, there is an urgent need to develop and validate reliable and minimally invasive biomarkers for CNS malignant tumors that can be used in diagnosis and monitoring. Circulating biomarkers in cerebrospinal fluid, including ctDNA, microRNAs and metabolites, hold promise for accurate assessment of CNS tumors. This review summarizes the current studies of those CSF biomarkers and their potential implementation in CNS malignant tumors.