Patrinia Villosa (P.V.) can cure diarrhea, and it can also relieve constipation. It is possible that tannins is one of the important components existing in leaves, stems and water-solution extracts of P.V. with the above functions. So the extraction technology of tannins from wild P.V. was studied, and the single factor test and orthogonal experiment design methods (L₉(3³)) were applied to analyze the influence of solid-liquid ratio, temperature and time on the extraction percentage of tannins from the water solution of P.V.. The effect of tannins on preventing diarrhea and relieving constipation was also studied. The results indicated that the optimum solid-liquid ratio, temperature and extraction time were respectively 1∶60, 45℃ and 6 h. Under this condition, the extraction percentage of tannins was 3.60%. Compared with P.V. polysaccharides, P.V. pectin and other samples, the animal test indicated that tannins from wild P.V. showed significantly high effect (P<0.05) on small intestine peristalsis of mice. Mouse feed with tannins reduces the times of defecation within 6 hours, and prolongs the time before initial defecation, and its function is just slightly inferior to P.V. Pectin. It shows that tannins is one of the most important components of wild P.V. for preventing diarrhea and constipation.