OBJECTIVE： To investigate the effects of Liuwei dihuang pills on heme oxygenase 1 （HO-1） in vascular tissue of diabetic model rats. METHODS： Rats were randomly divided into normal group， model group， Liuwei dihuang pills group （14    g/kg， ig， s.i.d） and HO-1 inhibitor zinc protoporphyrin （ZPP， 10 μmol/kg， ip， q.o.d）+Liuwei dihuang pills （14 g/kg， ig， s.i.d） group， with 12 rats in each group. Except for normal group， those groups were given streptozotocin intraperitoneally to induce diabetic model. After modeling， treatment groups were given relevant medicines， and normal group and model group were given normal saline intraperitoneally every 2 days for consecutive 4 weeks. The systolic blood pressure （SBP） of caudal artery and heart rate in rats were detected； the effects of Liuwei dihuang pills on the contraction response of thoracic aortic rings （TARs） irratated by phenylephrine （PE） were observed as well as the effects on the relaxation response of TARs irratated by acetylcholine （Ach） and sodium nitroprussiate （SNP）； mRNA and protein expression of HO-1 in vascular tissue were examined. RESULTS： Compared with normal group， SBP of model group increased， and the relaxation response of TARs to Ach irritation decreased while the contraction response of TARs to PE irritation increased （P＜0.05）. There was no statistical significance in mRNA and protein expression of HO-1 in vascular tissue （P＞0.05）. Compared with model group， the relaxation response of TARs to Ach irritation increased in Liuwei dihuang pills group， while the contruction response of TARs to PE irritation decreased； mRNA and protein expression of HO-1 increased in vascular tissue （P＜0.05 or P＜0.01）. Compared with Liuwei dihuang pills group， SBP of drug combination group increased continuously， while the relaxation response of TARs to Ach irritation decreased continously （P＜0.05）. There was no statistical significance in mRNA and protein expression of HO-1 in  vascular tissue （P＞0.05）. There was no statistical significance in heart rate among those groups （P＞0.05）. CONCLUSIONS： Liuwei dihuang pills can improve vascular reactivity disorder of diabetic model rats， which is likely related to the expression up-regulation of HO-1 in vascular tissue.