Objectives: This study was aimed to find the effect of Samiunkyungtang on inflammation and microflora in an ulcerative colitis animal model. Methods: We established four groups of normal, control, test 1, and test 2 and assigned 6 rats toeach group. The normal group was not treated by any process and fed by normal saline. The control & test groups were provided with 4% dextran sodium sulfate (DSS) treatment for 7 days. Samiunkyungtang extract was orally administered to test groups (test 1=25mg/kg, test 2 100mg/kg) 3 days after DSS treatment for 10 days. After DSS treatment finished, we sacrificed the mice and measured colon length and enzyme activities such as myeloperoxidase (MPO), alkine phosphatase (ALP), ${eta}$-glucuronidase, ${eta}$-glucosidase, chondroitinase, and tryptophanase. Results: The colon lengths of test 1 and 2 groups were longer than the control group (p<0.05). Histologically, the crypts and superficial epitheliums of test 1 and 2 groups were regenerated. Goblet cells from all test groups were retrieved. The inflammatory biochemical marker, MPO and ALP activities in all test groups were highly reduced (p<0.01) compared to the control group. The activities of fecal bacterial enzymes in test groups such as ${eta}$-glucuronidase, ${eta}$-glucosidase, chondroitinase, and tryptophanase were reduced compared to the control group (p<0.01). Conclusions: As a result of this experiment, Samiunkyungtang is considered to have an inhibitory effect on inflammation and fecal enzyme activity in DSS-induced colitis animal model. Our results indicate that Samiunkyungtang may possess therapeutic effect on the development of DSS-induced colitis.