Abstract: Meningeal metastasis (MM) is a fatal complication of lung cancer; conventional diagnostic modalities lack sensitivity. Cerebrospinal-fluid (CSF) liquid biopsy—an emerging, minimally invasive technology that can dynamically capture the intracranial tumor genome—has become the most representative liquid-biopsy substrate for genomic profiling of MM from lung cancer. It significantly improves both diagnostic yield and the precision of individualized therapy. This review systematically synthesizes current evidence on CSF liquid biopsy, delineating its value in guiding targeted treatment, tracking drug resistance, and prognosticating disease trajectory, with the goal of providing a rational framework for the clinical management of lung cancer meningeal metastasis.