Objective To investigate the role of endoplasmic reticulum (ER) stress in microvascular injury in hyperglycemic SD rats. Methods Healthy male SD rats were intraperitoneally injected with streptozotocin (STZ) to construct a hyperglycemic rat model. Blood pressure (BP) was measured by noninvasive caudal artery blood pressure measurement one month after the model was constructed, and body weight and random blood glucose level were monitored. Gene transcriptional levels of ER stress-related factors in rat mesenteric resistant arteries (MRAs) were measured by RT-PCR. Protein levels of GRP78/Bip, eNOS, Akt and IRS1 were detected by Western blotting. Results Random blood glucose level, systolic BP, diastolic BP and mean arterial pressure in the hyperglycemic group were significantly higher compared with the control group. RT-PCR showed that mRNA levels of ER stress main markers in rat microvascular tissue in the hyperglycemic group significantly increased (P<0.05). Western blotting showed that Bip protein level in the hyperglycemic group significantly increased (P<0.05) and phosphorylation of IRS1, Akt and eNOS significantly decreased (P<0.05). Conclusion Persistent hyperglycemia can induce hypertension in rats, which may be associated with ER stress-mediated microvessel dysfunction, impaired insulin signaling pathway in vascular tissue and decrease in eNOS activity.