Objective To observe the morphological changes of the retina at early stage of streptozotocin (STZ)-induced diabetes mellitus (DM) model, so as to assess the feasibility of using STZ-induced DM as an animal model of early diabetic retinopathy (DR). Methods Sixty-four male SD rats (body weight \[180±20\] g) were randomly divided into the CON and DM groups (n=32). Rats in DM group received intraperitoneal injection of 1% STZ once and those in the CON group were given same volume of citrate buffer in the same manner. The average body weight and blood glucose were similar in the two groups before intraperitoneal injection. The blood glucose, body weight, and other parameters were determined once a week after intraperitoneal injection. In the 10th week, the morphological changes of the retina were observed by H-E staining, stretched preparation of FITC-dextran perfused retinal blood vessels, and transmission electron microscopy in randomly chosen samples. Results The successful rate of STZ-induced DM model was 100%. The body weight of animals in DM group had no obvious increase after injection, and it even decreased at late stage. The body weight increased gradually in the CON group. The average body weight of DM group (\[169.9±26.9\] g) was significantly lower than that of the CON group (\[439.2±23.5\] g) in the 10th week (P<0.001). The average blood glucose of DM group (\[26.63±4.54\] mmol/L) was significantly higher than that of the CON group (\[6.37±0.49\] mmol/L) 72 h after injection (P<0.001). DM group had a blood glucose > 16.7 mmol/L and CON group had a blood glucose of 5.6-7.4 mmol/L throughout the 10 weeks. Retina H-E staining showed retinal capillary dilatation and interstitial edema in DM group in the 10th week, and the CON group had no obvious abnormalities. Stretched preparation of FITC-Dextran perfused retinal blood vessels showed vascular tortuosity and caliber irregularity in the DM group, but with no leakage, microvascular tumor or retinal non-perfusion area. The retinal vessel diameter was uniform and the branching was natural and smooth in the CON group. TEM results showed the following retinal ultrastructural changes in the DM group: thicker capillary basement membrane, digitation of capillary endothelial cells, mitochondrial swelling, cristae disruption, and vacuolar degeneration in capillary endothelial cells, bipolar cells and ganglion cells, mitochondrial swelling and cristae disruption in pericytes, decreased membranous disc (photoreceptor cell’s outer segment), and widened gap between membranous discs. Conclusion The retina morphological changes of early stage background diabetic retinopathy(BDR) can be found in the 10th week after STZ injection in rats, and STZ-induced DR model can be used as an early stage DR model; besides, the method is simple, economical, quick, with good reproducibility and high successful rate.