Objective To evaluate the method of detecting intestinal mucosal barrier damage, and investigatewhether propolis can lower glucose levels through repairing the intestinal mucosal barrier in diabetic rats. Methods A ratmodel of diabetes mellitus was established by administering a high-sugar and high-fat diet with a single intraperitonealinjection of 1% streptozotocin (STZ) at a dose of 40 mg/ kg. Then, the rats in the propolis treatment groups were orallysupplemented with 80 or 160 mg/ ( kg·d) propolis by gavage. The rats of control and model groups were orallysupplemented with soybean oil. After 4 weeks, a Roche glucometer was used to detect blood glucose concentration, highperformanceliquid chromatography was used to detect whole-blood hemoglobin A1c (HbA1c), ELISA was used to detectthe levels of plasma D-lactic acid (D-LA) and zonulin, western blotting was used to detect the expression levels of claudin-1, occludin, and ZO-1 in ileum and colon tissues, and the ultrastructure of ileum and colon tissues was examined bytransmission electron microscopy. Results The diabetic rat model was established successfully. After 4 weeks ofintervention, the blood glucose level in the 80 and 160 mg/ kg propolis treatment groups reached 17. 57 and 18. 24 mmol/L, and their HbA1c levels were 8. 94% and 8. 22%, respectively, which were significantly lower than that in the modelgroup ( P < 0. 05). Transmission electron microscopy showed that after propolis intervention, the tight junctions andadherens junctions of intestinal epithelium were improved. Western blotting showed that the expression levels of claudin-1,occludin, and ZO-1 in the ileum and the colon of the propolis intervention groups were significantly higher than in the modelgroup, in a dose-dependent manner ( P < 0. 05). ELISA data showed that the levels of plasma D-LA were 160. 03 and151. 18 ng/ mL in the 80 and 160 mg/ kg propolis intervention groups, respectively, and their plasma zonulin levels were650. 14 and 647. 60 μg/ mL, with no significant differences between them ( P > 0. 05). Conclusions Ultrastructuralobservation of the intestinal mucosal barrier and detection of the expression levels of proteins closely associated with theintestinal tissue have higher sensitivity than the serological determination of intestinal mucosal barrier function, so they canbe used as a reliable experimental method for studying the mechanism of the intestinal barrier repair associated with the hypoglycemic effect of propolis.