Objective: To observe the morphological changes of small artery after hemorrhagic shock and resuscitation in rats and expression of ICAM -1 and NOS. Methods: Specimen of tissues were taken in the ischemia 45 minutes and reperfusion for 1,3,6, 12,24 hours. By light microscope and electron microscope, observe the morphological changes of small artery. Using the immunohistochemistry technique to observe the expression of ICAM -1 and NOS in the small artery. Results: 1, light microscope and electron microscope: The injury degree of small artery in 45 min ischemia group was slight, the injury degree of reperfusion was more severe than ischemia group. The most severe cellular damage was found in 3 hour after reperfusion. Compared with the other tissues, the injury degree of small artery in brain was more slightly. 2, The expression of ICAM -1 and NOS was not increased in the normal group. But the expression of ICAM -1 and NOS in the ischemia and reperfusion were changed successively. The expression of NOS was increased after ischemia 45 min , it peaked after reperfusion for 1 hour, and began to decrease gradually after reperfusion for 3 hours. Compared with the control group, P<0.05. The expression of ICAM -1 was increased after reperfusion for 1 hour, it peaked after reperfusion for 3 hours, and lasted to 24 hours. Compared with the control group, P<0.05. Conclusion: KHemorrhagic shock and resuscitation can induce morphological changes of small artery, it can induce ischemia/reperfusion damage of small artery. 2, ICAM-1 and NOS