Abstract: In order to explore the effect of garlic extract on mouse diarrhea caused by swine Escherichia coli, the antibacterial effect, minimum inhibitory concentration（MIC） and minimal bactericidal concentration（MBC） of garlic extract on clinically isolated swine Escherichia coli were determined by bacteriostatic test in vitro. The mouse diarrhea model was established by intraperitoneal injection of swine Escherichia coli. After successful modeling, the mice were divided into blank group, model group, garlic extract low and high dose groups. The clinical symptoms of mice were observed after 7 days of continuous intragastric administration. The mortality rate, diarrhea rate, viscera index and fecal occult blood index were determined, and histopathological analysis was performed. The results showed that swine-derived Escherichia coli was very sensitive to garlic extract. The MIC of garlic extract to swine Escherichia coli was 31.25 mg/mL and the MBC was 62.5 mg/mL. Compared with the model group, the intake of mice in the low and high dose groups of garlic extract increased significantly or extremely significantly after administration（P＜0.05 or P＜0.01）. The body weight of mice in the low-dose garlic extract group increased significantly on the 1 st, 3 rd, 4 th, 6 th and 7 th day（P＜0.05）, and the body weight of mice in the high-dose garlic extract group increased significantly on the 1 st and 7 th day（P＜0.05）. The a low and high dose groups of garlic extract could significantly reduce the liver index of mice（P＜0.01） and the spleen index of mice（P＜0.05） and can make fecal occult blood test results negative. In the model group, the rupture of duodenal villi became shorter and fell off in large numbers, and the intestinal glands were obviously degenerated, and a large number of inflammatory cells were infiltrated in the mucosa. The duodenal mucosal epithelium and gland structure of mice in the high and low dose garlic extract groups were basically complete, and there was a small amount of inflammatory cell infiltration in the lamina propria glandular stroma.It indicated that garlic extract had obvious antibacterial effect on swine Escherichia coli in vitro, and could effectively inhibit mouse diarrhea caused by swine-derived Escherichia coli.