Abstract: OBJECTIVE To observe the effect of Astragaloside-Ⅳ (AS-Ⅳ) on oxygen stress and EMT of peritoneal mesothelial cells (PMCs) HMrSV5， explore the function of ROS in EMT and regulatory mechanism of AS-Ⅳ. METHODS We used peritoneal dialysis solutions (PDS) with high glucose concentration to establish oxygen stress cell model of HMrSV5. Morphologic alterations of cells were observed and MTT assay was used to detect cell viability. DHE fluorescent probes were loaded to label secreted ROS. EMT-associated proteins were expressed by western blotting analysis. RESULTS ①40 or 50μg/mL AS-Ⅳ increased the viability of HMrSV5 (P<0.05). Cell viability was supressed due to the longstanding effect of PDS and high glucose concentration， notably in intervention of PDS containing 4.25% glucose for 48h. Phenotypic changes of HMrSV5 characterized by cell elongation and losing cobblestone like feature. ②40μg/mL AS-Ⅳ could suppress morphologic changes of cells， decrease ROS expression in model group (P<0.05)， upregulate the protein expression of E-cadherin and ZO-1 while downregulate α-SMA. Furthermore， the phosphorylation of Smad2/3 protein was inhibited. ③ 5mmol/L NAC had the similar effect on EMT of PMCs. CONCLUSION PDS with high glucose concentration can suppress cell viability and induce EMT of PMCs by upregulating ROS expression and activation of Smads pathway. AS-Ⅳ can reduce ROS generation， suppress the phosphorylation of Smad2/3 and thus， inhibite the EMT of PMCs.