Objective：To establish a chronic malignant transformation model of immortalized human bronchial epithelial cell line BEP2D by low dose cigarette smoke condensate (simulating smoking environment).Methods: The chronic dose of cigarette smoke condensate was determined by MTT assay and the colony formation test of BEP2D cells. BEP2D cells were exposed to cigarette smoke condensate once or for multiple times; unexposed cells were taken as control. The malignant tendency of BEP2D cells was identified by antiserum experiment and the malignant features of transformed BEP2D cells were identified by semisolid agar culture. The differentiation ability of BEP2D cells in antiserum experiment and the colony forming rates of BEP2D cells were compared between different groups. Results: The BEP2D cells were exposed to 0.5,1 and 2 μl/ml of cigarette smoke condensate once or for multiple times and were cultured for 25 generations;the differentiation abilities of BEP2D cells(the 25th generation) was significantly different between the cigarette smoke condensate exposed groups (at 0.5,1 and 2 μl/ml) and the normal control group (P<0.05). The cell malignant transformation model was successfully established in the cells of the 38th generation; the cells had multilayer growth and had no contacting inhibition, with chromosome abnormality. The colony forming rates in the semisolid agar culture test was significantly higher in all smoke condensate exposed groups than in control group(P<0.05). The doseresponse relationship showed a good linear correlation (r=0.969, y=42x, P<0.05). Conclusion: The malignant transformation of immortalized human bronchial epithelial cells can be successfully induced by cigarette smoke condensate at 0.52 μl/ml, which offers an ideal model for simulating smoking environment induced chronic malignant transformation.