Objective:To investigate insulin on the viability of ischemic random dorsal flap in the SD rats,and discuss the correlation between the protection of the ischemic-reperfusion injury and the enhancement of viability on the random flap of rats . Methods:Rat model with caudally based random dorsal flap measuring 6.0 cm×1.5 cm was constructed,which were divided into 2 groups:treated group(Group A,n=16)with single-dose insulin 0.1 U(1 ml)injection under the flap afer operation and control group(Group B,n=16)with saline. Before injection and 1 h,2 h,3 h after injection,levels of blood glucose were measured. At 24 h postoperatively,the amount of superoxide dismutase(SOD),glutathione(GSH)and malondialdehyde(MDA)in the flap tissue samples were measured. The flap viability and microvascular expression were measured at 7th day after operation. Results:There was not significant decrease in blood glucose in treated group compared with control group(P > 0.05). At 24 h postoperatively,there was significant decrease in MDA in treated group compared with control group,and significant increase in SOD and GSH(P < 0.05);at 7th day after operation,the viability in treated group was significantly higher compared with that in the control group[(73.963±8.649)% vs(56.175±4.250)%,P < 0.01]. Conclusion:Topical use of insulin markedly improved the viability of random dorsal flap of SD rats,which may be involved in the reduction of ischemia-reperfusion injury.