Objective To investigate the effects of HO-1/CO and iNOS/NO in postconditioning on ischemia/reperfusion injury in rats.Methods Thirty-six SD rats were divided into three groups with twelve animals in each group at random:sham-operation group,control group and expremental group.Blood and left kidney was collected after Twenty-four hours’reperfusion.Nitric oxide(NO),activity of superoxide dismutase (SOD) and content of malondialdehyde (MDA),carbon monoxide hemoglobin(HbCO) in blood were examined;heme oxygenase-1(HO-1)’s and iNOS’s expressions in rat kidney tissue were detected by immunohistochemisty and morphometry computer image analysis.Structure of the kidney was evaluated under light microscopy.Results Twenty-four hours after reperfusion, Blood N0,MDA concentrations were significantly increased, SOD activity was significantly decreased a in group Ⅱ as compared with groupⅠand Ⅲ(P<0.05 or P<0.01).Expression of HO-1 was obviously higher while induced Nitric Oxide Synthase(iNOS) was significantly lower in group Ⅲ than that in group Ⅱ.Expression of HO-1 and iNOS were significantly higher in group Ⅱ as compared with groupthan that in group Ⅰ..The damage to renal tubules was significantly attenuated in group Ⅲ compared with group Ⅱ.Conclusion Postconditioning could protect the renal IRI by up-regulating HO-1/CO and inhibiting the expression of iNOS/NO.