Abstract: In recent years， organ-on-a-chip technology has attracted increasing attention in the field of neurological disease research， particularly for its unique advantages in simulating the structure and function of the blood-brain barrier （BBB）. This technology uses microfluidic platforms to arrange key cell types， such as brain microvascular endothelial cells， pericytes， and astrocytes， in an orderly manner， enabling a highly biomimetic reconstruction of the BBB microenvironment in vitro. Compared with traditional Transwell models， organ-on-a-chip systems offer superior controllability and dynamic monitoring capabilities， making them suitable for drug permeability assessment and mechanistic studies. In the context of brain metastasis， these chips allow for the observation of tumor cell transmigration across the BBB and the analysis of their interactions with intracerebral cells， thereby supporting drug screening and therapeutic strategy optimization. This review introduces the fundamental structure and functions of the BBB， summarizes the technical principles， design strategies， and current challenges in BBB chip modeling， and highlights representative applications in brain metastasis research， providing new technological tools and insights for advancing precise diagnosis and treatment of brain metastases.

Key words: Organ-on-a-chip, &emsp, Blood-brain barrier, &emsp, Brain metastasis, &emsp, Drug screening