Abstract： Objective： To observe the effect of total Panax notoginseng saponins(tPNS) on apoptosis of bone marrow mesenchymal stem cells(BMSCs) induced by hydrogen peroxide(H2O2) in vitro，and to explore the molecular mechanism of tPNS through ERK1/2 pathway. Methods： BMSCs of SD rats were isolated and cultured in vitro by whole bone marrow adherent method. After BMSCs were treated with different concentrations of tPNS(25 ， 50 ， 100 and 200 μg/mL) for 24 hours，the cells were incubated with 500 μmol /L H2O2 for 24 hours to induce apoptosis. MTT assay was used to detect cell viability，and flow cytometry was used to detect cell cycle. After pretreatment with 100 μg/mL tPNS for 24 hours and treatment with ERK1/2 inhibitor PD98059(25 μmol/L) for 1 h，and the cells were incubated with 500 μmol/L H2O2 for 24 hours to induce apoptosis. The apoptosis rate was detected by Annexin V-FITC/PI double staining assay，and the Western Blot was used to detect the expression of ERK1/2 and its protein phosphorylation. Results：The survival rates in the other groups were significantly decreased when compared with those in the control group(P＜0.01)；the 100 μg/mL group and the 200 μg/mL tPNS group could significantly increase the survival rate of BMSCs when compared with that in the control group(P＜0.01)， and the 100 μg/mL has better effect，and therefore，the 100 μg/mL tPNS group with the best optimal concentration was used for further study. After BMSCs were treated with tPNS for 24 hours，the proportions of cell number in the cell cycle of G2 + S in the 100 μg/mL group and the 200 μg/mL tPNS group were significantly increased when compared with that in the H2O2 group(P＜0.05)，and the number in the 100 μg/mL tPNS group was larger than that in the 200 μg/mL tPNS group；there was no significant difference being found between the tPNS groups with the other concentrations and the H2O2 group(P＞ 0.05). The apoptosis rates in the other groups were increased when compared with those in the control group(P＜0.01)；the tPNS group could significantly decrease the apoptosis rate of BMSCs when compared with that in the H2O2 group(P＜0.01)； the tPNS + PD98059 group could significantly increase the apoptosis rate of BMSCs when compared with that in the tPNS group(P＜0.05). The H2O2 group and the tPNS + PD98059 group can significantly down- regulate the expression of ERK1/2 protein phosphorylation when compared with that in the control group(P＜0.01)； the tPNS group and the tPNS + PD98059 group can significantly up- regulate the expression of ERK1/2 protein phosphorylation when compared with that in the H2O2 group(P＜0.01)；there was no significant difference being found in the comparison between the tPNS group and the tPNS+ PD98059 group. Conclusion：tPNS has protective effect on the apoptosis of BMSCs induced by H2O2，and its mechanism may be related to the promotion of ERK1/2 protein phosphorylation.