Objective:The pathological changes of urinary tract were observed after the treatment of infectious stone by vanillic acid. Methods:40 male Wistar rats were randomly divided into blank control group, infectious stone group, vanillic acid group and acetohydroxamic acid group. Blank control group:4 male Wistar rats were fed without special treatment. Infectious Stone Group:12 male Wistar rats were implanted with 4 mm bacteria bearing foreign body in the front of the polyurethane vein indwelling needle infected with Proteus mirabilis into the bladder to induce the formation of infection stone. In the vanillic acid group, after the model were establishmented, 12 male Wistar rats were treated with vanillic acid at 50mg/kg?d for 3 weeks. Acetohydroxamic acid group:after the model were establishmented,12 male Wistar rats were treated with acetohydroxamic acid at 12.5mg/kg?d for 3 weeks. The rats were killed 21 days later.The kidney, ureter and bladder were fixed in 10％ paraformaldehyde solution for 24 hours. The specimens were embedded in paraffin, and the pathological analysis was carried out after HE and immunohistochemical staining. Results:In addition to the blank control group, the other three groups of rats had calculus formation in the bladder. No obvious pathological changes were found in the kidney, ureter and bladder in the blank control group, and inflammatory reactions were found in the other three groups:severe urinary tract inflammation was found in the infectious stone group, followed by acetylhydroxamic acid group. In the vanillic acid group, the pathological changes of urinary tract were the lightest, with a small amount of inflammatory cell infiltration and mucosal hyperplasia, but no serious pathological changes such as mucosal loss. The expression of Tamm-Horsfall Protein (THP) in the ascending branch of loop of Henle and the proximal part of distal tubule in vanillic acid group was not significant compared with that in the infectious stone group and acetohydroxamic acid group. Conclusion:Proteus mirabilis and its infective stones can lead to the damage of urinary epithelium. Vanillic acid can reduce the inflammatory lesions of urinary tissue.