Abstract Objective Matraine, a main ingredient of sophora, can inhibit the proliferation of many tumor cells such as K562 and HL-60. This study was designed to investigate the effect of matrine on acute lymphoblastic leukemia (ALL) cells and its possible mechanisms. Methods The samples were obtained from 24 children with initial ALL. The ALL cells were co-cultured with matrine. The inhibition effect of the proliferation of ALL cells was detected by the MTT assay. A flow cytometer (FCM) was used to detect the expression of Bcl-2 in ALL cells. Results Compared with the controls without matrine treatment ( 0.84± 0.27), the OD values (reflecting the survival cell amount) were reduced significantly after 48 hrs of different concentrations of matrine incubation ( 0.73± 0.16 at 0.1 mg/ml, 0.58± 0.15 at 0.2 mg/ml, 0.32± 0.16 at 0.5 mg/ml, and 0.24± 0.14 at 1.0 mg/ml). The positive rate of Bcl-2 protein was down-regulated significantly from ( 25.0± 5.8)% in the untreated controls to ( 21.3± 6.1)% in the cells treated with 0.1 mg/ml matrine, and ( 18.2± 3.7)% for 0.2 mg/ml, ( 14.5± 4.0)% for 0.5 mg/ml and ( 10.0± 3.2)% for 1.0 mg/ml at 48 hrs of incubation. Conclusions Matraine can inhibit the proliferation of ALL cells, and the possible mechanism may be associated with the down-regulated Bcl-2 expression in ALL cells.