Objective:To investigate the response of human pulmonary artery smooth muscle cells(PASMCs)to hypoxia with or without Xinmailong injection(XML),and explore the mechanism for XML to remit pulmonary artery hypertension(PAH). Methods:Na2S2O4 was used for building the hypoxic pulmonary artery smooth muscle cell model. The changes of apoptosis rate and apoptosis associated genes were detected by flow cytometry and realtime PCR,respectively,and membrane potentials and cytoplasmic Ca2+ under hypoxic stimulation were investigated by a laser scanning confocal microscope. Results:Under hypoxia condition,the proliferation of PASMCs was significant compared with that of the control group(P < 0.05),however,this effects can be markedly retarded by the treatment of XML(P < 0.05). Moreover,under hypoxia condition,Bcl-2 expression in PASMCs was obviously increased,while Bax expression was decreased when compared with those of the control group(P < 0.05). Noteworthily,XML can reverse both Bcl-2 and Bax expression induced by hypoxia(P < 0.05). In addition,XML stabilized the membrane potential and reduced the cytoplasmic Ca2+ under the hypoxic condition. Conclusion:Hypoxia leads to the proliferation of PASMCs,depolarization of membrane and increase of cytoplasmic Ca2+. The Chinese medicine XML can reduce all the effects induced by hypoxia,thereby our work might provide the experimental evidence for therapeutic strategy for pulmonary artery hypertension.