AIM To observe the treatment effects of Jianpiling in chronic ulcerative colitis(CUC) as well as its mechanism of strengthening the spleen and supplementing the qi. METHODS Three groups of CUC patients totally 420 were formed as Jianpiling group, SASP group and Bupiyichang pill group clinically. Pharmacological experimental aspect involved detecting the motion states (frequency and amplitude) of isolated intestines of rabbits, propelling power of small intestine confirmed with charcoal powder, and ensuing effects on the immune function and histopathology of CUC rat. RESULTS Clinically there was an apparent therapeutic difference among Jianpiling, SASP and Bupiyichang groups( P <0 01), with curative rates of 67 7%, 30 0% and 48 3% respectively. Pharmacologically Jianpiling inhibited peristalsis frequency and amplitude of both jejunum and ileum of rabbits to a great extent, antagonized both rigid contraction caused by acetylcholine or barium chloride and adrenaline induced inhibition of small intestines, reduced greatly the antibody against large intestine and IgG level in rat blood, and increased the weight of the immune organs of rat such as thymus, spleen, etc. CONCLUSION Jianpiling's therapeutic effects on diarrhea of CUC was done by means of inhibiting propelling power of intestines, increased cellular immune functions, suppression of humoral immune activities. In addition its direct actions against the smooth muscle spasm and acetylcholine M receptor relieved pain.