Objective To investigate the mechanism of action of paeonol in alleviating colitis-cancer transformation in mice based on the STAT-3/NF-κB/ICAM-1 signaling pathway. Methods A mouse model of colitis-cancer transformation was established. ELISA was used to measure the serum levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and interleukin-10 (IL-10); Western blot and immunohistochemical staining were used to measure the protein expression levels of signal transducer and activator of transduction 3 (STAT-3), nuclear factor κB (NF-κB) p65, and intercellular adhesion molecule 1 (ICAM-1) in colon tissue. Results The paeonol treatment group had significant alleviation of inflammatory cell infiltration and gland disorder in the colon under a light microscope. Paeonol significantly reduced the number of tumors, tumor mass, spleen index, and the serum levels of TNF-α, IL-6, and IL-1β (P<0.05), significantly increased the serum level of IL-10 (P<0.05), and significantly reduced the expression levels of STAT-3, NF-κB p65, and ICAM-1 in the colon (P<0.05), and middle-dose paeonol had the best effect (P<0.05). Conclusion Paeonol can effectively alleviate inflammatory response in mice with ulcerative colitis, possibly by regulating the STAT-3/NF-κB/ICAM-1 signaling pathway.