Abstract: Objective To investigate the roles of helper T cells (Th), regulatory T cells (Treg) and calprotectin in the pathogenesis of ulcerative colitis (UC) in the rat model. Methods Thirty rats were randomly divided into normal control (NC) group and UC model (UC) group. The rats of UC group were replicated using the mixed solution of 2, 4,6 trinitrobenzene sulfonic acid (TNBS) / ethanol through the intestinal tract. The rats of NC group were given NaCl solution enema. Three weeks after UC modeling, the morphology changes of colon tissue were observed. The serum levels interleukin (IL)-1β, IL-10, IL-17, IL-23 and calprotectin (CP) were detected by enzyme-linked immunosorbent assay. The changes of Treg in peripheral blood were measured by flow cytometry. The expressions of IL-17, CP, and transcriptional regulatory proteins of decision Treg cell differentiation and function (FoxP3) in colon tissue were detected by Western blot and immunohistochemistry. Results UC group was observed with obvious colon tissue injury and inflammatory cells infiltration in intestinal tissue, compared with NC group, the expression of IL-1β,IL-17,IL-23,CP in serum were increased, while the expression of IL-10, the number of Treg were decreased in UC group (P<0.05 or P<0.01). Compared with NC group, the expression of IL-17, CP in colon tissue were significantly increased in UC group (P<0.05), and the expression of FoxP3 was increased (P<0.05). Conclusion Expressions of calprotectin, IL-17 of intestinal tissue, serum are increased in rat of ulcerative colitis, which to lead to the imbalance of Treg/Th17 cells, and elevate inflammatory responses. These factors have promote the occurrence and development of ulcerative colitis.