This study was aimed to explore the effect of midazolam on mantle cell lymphoma cell line JeKo-1 and the relevant mechanisms. Effects of midazolam on the proliferation and apoptosis of JeKo-1 cells were observed by CCK8 assay and flow cytometry, respectively. Effect of midazolam on the expression of BCL-2, cytochrome C (Cyto-C), pro-caspase-9, pro-caspase-8 and pro-caspase-3 protein were detected by Western blot. The results showed that midazolam could inhibit the growth of JeKo-1 cells significantly and the concentration of 50% growth inhibition (IC50) at 48 hours was approximately 40 µmol/L. After treatment with 20, 40, 80 µmol/L midazolam for 48 hours, a dose-dependent apoptosis of JeKo-1 cells could be observed. Meanwhile, a dose-dependent reduction of BCL-2, pro-caspase-9 and pro-caspase-3 protein expression and increase of Cyto-C protein expression in JeKo-1 cells were found, but the expression of pro-caspase-8 protein did not change. It is concluded that midazolam possibly initiates the mitochondrial pathway, not the death receptor pathway, by reducing the expression of BCL-2, leading in turn to the releasing of Cyto-C in mitochondria, then activating caspase-9 and caspase-3 protein, triggers the caspase cascade, and induces the apoptosis of JeKo-1 cells ultimately.