Objective To investigate the protective effect of human amniotic mesenchymal stem cells(hAMSCs)on pulmonary microvascular endothelial cell(PMVECs)through observing the effects of prolifer-ation,apoptosis and inflammatory response after PMVECs injury induced by pine sawdust smoke solution.Methods HAMSCs and rat PMVECs were isolated and cultured.The flow cytometry and immunofluores-cence were used to identify hAMSCs and PMVECs respectively.The experimental grouping:control group(normal cultured PMVECs),smoke group(PMVECs injury induced by pine sawdust smoke solution),smoke+hAMSCs group(after PMVECs was injured by smoke solution,hAMSCs and PMVECs were co-cul-tured in Transwell culture system).The proliferative activity of PMVECs after co-culture for 12,24 h was measured by cell counting kit-8(CCK-8),the apoptosis of PMVECs was measured by flow cytometry,and the ex-pression levels of TNF-α and IL-6 were detected by enzyme-linked immunosorbent assay(ELISA).Results hAMSCs and PMVECs were successfully isolated and cultured,and the hAMSCs surface markers CD105(95.4％),CD73(99.8％)and CD90(99.8％)were identified as strongly positive expression,while CD34,CD45,CD14,CD19 and HLA-DR were weakly expressed(1.96％in total).The vascular endothelial cell mark-er CD34 in PMVECs was positively expressed,moreover its combination with aggulutinin BSI was also posi-tive.At the observation time point of 12,24 h co-culture,compared with the Control group,the proliferation activity of PMVECs in the Smoke group was inhibited(P＜0.05),and the cellular apoptosis was increased(P＜0.05),the TNF-α and IL-6 expression levels were up-regulated(P＜0.05);the phenomena of PMVECs proliferation activity inhibition,apoptosis increase and inflammatory factor expression level up-regulation in the Smoke+hAMSCs group were reversed compared with the Smoke group(P＜0.05).Conclusion After PMVECs are injured by smoke solution,hAMSCs could decrease the PMVECs inflammatory factors expres-sion,promote its proliferation activity and inhibit its apoptosis,thus play the protective effect on PMVECs.