The invention provides a novel Chinese medicine composition for treating ulcerative colitis and a preparation method thereof. The composition is mainly prepared from the following raw materials including, by weight, 5-15 parts of codonopsis pilosula, 1-10 parts of radix sophorae flavescentis, 1-10 parts of costustoot, 3-9 parts of myrobalan meat and 1-8 parts of salt oriental waterplantain rhizome. The preparation method of the Chinese medicine composition comprises the following steps that all the raw materials are taken by weight; water is added for decoction, or extraction is conducted through ethanol water, and a decoction solution or an extraction solution is obtained; the obtained decoction solution or the obtained extraction solution is filtered, so that filtrate is obtained; and the filtrate is subjected to concentration, so that clear paste is obtained. The invention further provides application of the Chinese medicine composition in preparing medicine for treating inflammation. Rat colon tissue pathological damage caused by trinitro-benzene-sulfonic acid can be antagonized through the Chinese medicine composition, the overall inflammatory immune reaction can be reinforced, appearance signs such as animal hemafecia, diarrhea, little activity and the like are obviously improved, and the curative effect is obvious.