Objective:To observe the change of peripheral PMNS CD18 at the early stage of rat lung reperfusion injury.Methods:Twenty SD rats were divided randomly into 4 groups:control group,ischemia group,reperfusion 30 min group and reperfusion 60 min group.The left lung wet/dry mass(mW/mD) ratio,the pulmonary artery pressure and the level of circulating PMNS CD18 of animals in each group were measured. Results:The mW/mD ratio and the pulmonary artery pressure of both the reperfusion 30min and 60min group were higher than those of the control group(P<0.01),respectively.The level of PMNS CD18 of the reperfusion 60min group increased significantly compared with that of the reperfusion 30min group(P<0.01).The PMNS count of the circulating blood was lower in the reperfusion 60 min group than in the control group (P<0.05).Conclusion:The level of PMNS CD18 increases and the count of PMNS decreases at the early stage of lung reperfusion injury.