Objective：To investigate the cell proliferation and cell cycle and the expression of cyclin D1 in the primary cultred airway smooth muscle cells（ASMC） in murine model of asthma. Methods：The murine asthmatic model was established and the primary ASMC were cultured. The primary ASMC of normal mice were chosen as control group. The cell proliferation was detected by MTT. The cell cycle was measured by FCM, and the expression of cyclin D1 was measured by FCM. Results：Compared with the normal ASMC line,the cell proliferation and the percentage of S phase of asthmatic ASMC line was significantly increased（P < 0.05）. The expression of cyclin D1 was significantly increased compared with the normal cell line. Conclusion：The proliferation of ASMC is increased in the progression of airway remodeling in asthma and cyclin D1 may contribute to this progression.