Objective:To explore the distribution of TCM syndromes in ulcerative colitis (UC) and their relationship with the characteristics colonoscopy mucosal and histological grading.Methods:A retrospective analysis was conducted on the TCM syndrome classification, colonoscopy mucosal images, and histological grading of 303 UC patients at Henan Provincial Traditional Chinese Medicine Hospital from January 2023 to January 2024. The characteristics and correlation of colonoscopy mucosal images and histological grading in UC patients with different TCM syndrome types was explored.Results:The top three TCM syndrome types of UC patients were large intestine damp-heat syndrome (24.75%), spleen-qi deficiency syndrome (21.12%) and liver-stagnation and spleen-deficiency syndrome (19.80%). Compared with the syndrome of spleen deficiency and dampness accumulation, heat and toxin exuberance, cold and heat mixed syndrome, liver stagnation and spleen deficiency syndrome, spleen and kidney yang deficiency syndrome, spleen qi deficiency syndrome, yin and blood deficiency syndrome, blood stasis and intestinal collateral syndrome, patients with colonic damp-heat syndrome type Ⅰ accounted for the highest proportion ( χ2=12.79, 16.24, 4.26, 16.54, 11.53, 14.16, 7.75, 10.91, P<0.05). The proportion of type Ⅲ patients was the lowest ( χ2=30.57, 33.59, 12.71, 23.63, 7.90, 19.88, 18.31, 17.31, P<0.05). Among the patients with different TCM syndrome types, the proportion of large intestine damp-heat syndrome in histological grade Ⅳ was the highest (66.67%), the proportion of blood stasis and intestinal meridian syndrome in histological grade Ⅲ was the highest (53.33%), the proportion of liver stagnation and spleen deficiency syndrome in histological grade Ⅱ was the highest (50.00%), and the proportion of spleen and kidney yang deficiency syndrome in histological grade Ⅰ was the highest (40.00%). Spearman correlation analysis showed that the large intestine damp-heat syndrome was significantly correlated with the characteristics of colonoscopy mucosal image and histological grade ( r=-0.563, 0.612, respectively, all P<0.001). The syndrome of spleen deficiency and dampness accumulation, heat and toxin exuberance, yin and blood deficiency, blood stasis and intestinal collateral were significantly positively correlated with the characteristics of colonoscopy mucosa ( r=0.373, 0.342, 0.263, 0.331, all P<0.05). The syndrome of liver stagnation and spleen deficiency and spleen and kidney yang deficiency were significantly negatively correlated with histological grade ( r=-0.417, -0.425, all P<0.01). Conclusions:The main TCM syndromes are large intestine damp-heat syndrome, spleen-qi deficiency syndrome and liver-qi deficiency syndrome, which are significantly correlated with the mucosal features and histological grade of colonoscopy. Colonoscopy and histophiologic examination can be used as objective indicators for TCM syndrome differentiation.