Objective To study the short-term oral toxicity and the effect of zinc oxide nanoparticles on intestinal immune in rats. Methods Weaning rats were randomly divided into 4 groups:control group, low, medium and high-dose groups (10 male and famale rats in each group). Zinc oxide nanoparticles were intragastrically administered at doses of 87.5,5 and 350 mg/kg BW for 28 days, respectively. Blood samples were collected on day 29 for measurement of hematology and clinical biochemistry. Animals were euthanized for necropsy, and selected organs were weighed and fixed for histological examination. Flow cytometric analysis of lymphocyte subsets of Peyer's patch and the level of secretory immunoglobulin A (SIgA) in intestinal fluid were detected. Results There were no toxicologically significant changes in clinical signs, body weight, food consumption, necropsy findings and organ weights, hematological and clinical biochemical values. Histopathological examination showed an increased incidence of focal epithelial cell exfoliation in gastric mucosa, inflammatory cell infiltration and edema in gastric submucosa, and villous epithelial cell exfoliation in small intestine. Compared with the control group, the number of lesions in the high dose group increased significantly. Lymphocytes phenotyping analysis showed a significant increase in percentage of T lymphocytes and decrease in percentage of natural killer(NK)cell in Peyer's patch. The concentration of SIgA had no significant difference between dose groups(P＞0.05). Conclusion The ingestion of zinc oxide nanoparticles can cause gastrointestinal mucosal damage and can affect the intestinal immune index in rats, at 350 mg/kg BW dose.