Objective To investigate the effects of 20%mannitol injection on the proliferation and apoptosis of hu-man lung squamous carcinoma cell line NCI-H292 and its possible mechanisms.Methods NCI-H292 cells were incubated with 20%and lower concentrations of mannitol.Cell proliferation and viability were detected by CCK-8 assay.Cell apoptosis was detected by flow cytometry and the expression of mitochondrial apoptosis pathway-related proteins Bcl-2 and Bax was detected by Western blot.Results Compared with the control group,mannitol inhibited cell proliferation in a dose-and time-dependent manner(P＜0.05),20%mannitol could induce cell ap-optosis(P＜0.05).The expression level of Bcl-2 was significantly reduced,while that expression level of Bax was significantly increased in cells incubated with 20%mannitol(P＜0.05).Conclusions Clinically used 20%man-nitol injection can induce apoptosis of lung squamous carcinoma cell line NCI-H292.Its mechanism is related to mi-tochondrial pathway-related proteins Bcl-2 and Bax.