Abstract： Objective To explore effect of erythropoietin on the caspase-3 subfamily in preventing apoptosis of human umbilical vein endothelial cells (HUVECs) induced by oxidized-low density lipoprotein (ox-LDL). Methods Third-sixth passages of HUVECs were used. Two experiments were conducted. In the first experiment, there was a blank control group, ox-LDL control group (100 mg/L, incubated for 48 hours), and low, medium, and high recombinant human erythropoietin (rhEPO) groups (6.25, 25.00, 100.00 kU/L rhEPO incubated for 24 hours+100 mg/L ox-LDL incubated for 48 hours). Another experimental protocol consisted of groups of the cells pretreated with either caspase-3 inhibitor DEVD-CHO, or caspase-8 inhibitor z-IETD-fmk, or caspase-9 inhibitor z-LEHD-fmk of 25 μmol/L for 24 hours, then HUVECs were exposed ox-LDL (100 mg/L) incubated for 48 hours. The activity of caspase-3, caspase-8, or caspase 9 was determined by caspase colorimetric assay. The cell survival rate was assessed with methyl thiazolyl tetrazolium (MTT) method. The positive expression rate of caspase-3 and apoptotic rate were measured by flow cytometer. Results The activity of caspase-3 was significantly decreased and cell survival rate was increased in the caspase-3 inhibitor group (both P<0.05). The activity of caspase-8 was decreased in the caspase-8 inhibitor group (P<0.05), but the cell survival rate was not significantly different from that of ox-LDL group (P>0.05). The activity of caspase-3 or caspase-9 was lower and cell survival rate was higher in the caspase-9 inhibitior group than that of ox-LDL group (all P<0.05). The pretreatment with rhEPO led to decreased activity of caspase-3, caspase-9, positive expression rate of caspase-3 and apoptotic rate in a dose-dependent manner compared with ox-LDL group (all P<0.05), but the activity of caspase-8 showed no significant difference from rhEPO pretreatment groups (all P>0.05). Conclusion These results demonstrate that rhEPO can significantly inhibit the activity of caspase-3 or caspase-9 in endothelial cell apoptosis in a dose-dependent manner. Activation of caspase-3 or caspase-9 is involved in ox-LDL-induced HUVECs apoptotic signaling pathway, but caspase-8 is not involved.