Objective:To observe the effects of recombinant human erythropoietin(rhEPO)on skin flap in the SD rats,and discuss the possible mechanism. Methods:A dorsal,caudally based random flap measuring 2 cm × 9 cm was created in all 24 SD rats which were divided into two groups:control group(Group A,n=12)with saline injected through the intraperitoneal route after operation,and treated group(Group B,n=12)with single-dose rhEPO 5 000 IU/kg injected through the intraperitoneal route after operation. At 24 th hour postoperatively,the myeloperoxidase(MPO)activity and the amount of malondialdehyde(MDA) were evaluated on the flap tissue samples of 6 rats chosen randomly. The flap viability and immunohistochemical(CD34)methods which can evaluate the microvascular network were applyed on the rest rats at day 7 after operation. Results:There was significant decrease in MPO and MDA in treated group compared with control group,and a significant increase in the flap viability in treated group was observed(P < 0.05). Conclusion:rhEPO can decrease the MPO activity and amount of MDA in the tissues of random flap at the first 24 h after operation and increase microvessel density and viability at day 7 after operation.