Abstract: Lung cancer is one of the most common malignant tumors. Brain metastasis, especially meningeal metastasis, is a fatal complication of lung cancer. The sensitivity of traditional diagnostic methods for this disease is limited. As a new technology, cerebrospinal fluid liquid biopsy can noninvasively and dynamically detect the molecular characteristics of intracranial tumors. Cerebrospinal fluid directly contacts the central nervous system lesions. It contains more unique and representative tumor-derived molecular information compared with those obtained from other body fluids such as blood for lung cancer meningeal metastasis, thus remarkably improving the diagnosis and personalized treatment of lung cancer meningeal metastasis. This work reviews the research progress on cerebrospinal fluid liquid biopsy in lung cancer brain metastasis and explores its value in guiding targeted therapy, delineating drug resistance, and evaluating prognostic progression to provide new directions for the clinical diagnosis and treatment of lung cancer brain metastasis.