Abstract: To investigate the effect and mechanism of Kuijieling decoction(KD) on the apoptosis of polymorph nuclear neutrophil (PMN) in the model of ulcerative colitis,the rat model of ulcerative colitis was induced by 100 mg/kg of 2,4,6-trinitrobenzene sulfonic acid (TNBS) enema.The experimental animals were randomly divided into Kuijieling treatment group (including high,medium and low dosage),model control group,and mesalazine positive control group.Each group, except for the normal group，was treated from 3rd day with an enema of 0.9% saline、mesalazine and KD respectively.The rats were sacrificed 10 days later.The histomorphological changes of the colon were evaluated by naked eyes and microscope.The apoptosis of PMN was tested by flow cytometry and the content of IL-8，NO and ICAM-1 was detected with ELISA in the peripheral blood of rats.There were significant effects on ulcerative colitis and in increasing the apoptosis of PMN in the KD (9.2 and 18.3 g·kg^-1·d^-1) groups and mesalazine solution group (P<0.05).The apoptosis were positively correlated with inflammation in the model of colitis in a dose-dependent relationship with KD.Compared with the model group，the contents of IL-8，NO and ICAM-1 were decreased in the groups of KD (9.2 and 18.3·kg^-1·d^-1) and mesalazine solution (P<0.01).The correlation coefficients between the apoptosis and IL-8，NO，ICAM-1 were -0.792 6，-0.705 1 and -0.593 7 respectively.The results demonstrated that Kuijieling decoction exerted a therapeutic effect on the rat model of ulcerative colitis possibly by reducing the content of IL-8，NO and ICAM-1 to increase the apoptosis of PMN.