Abstract: Objective To explore the clinical significance and expression ofβdefensin-2 of colonic mucosa in patients with ulcerative colitis (UC).Methods 30 patients with UC enrolled from May 2009 to December 2012 in our hospital were selected as UC group,30 patients with irri-table bowel syndrome (IBS)were in IBS group and 30 healthy people were in control group.Elec-tronic colonoscopy was applied in all groups.RNA was extracted immediately from part of the col-lected biopsy tissues for PT-PCR detection,and the rest biopsy tissues were used for HBD-2 im-munohistochemical staining by SP method.HBD-2 mRNA expression level,positive rate and inten-sity of HBD-2 of colonic mucosa in patients of three groups were compared.Results HBD-2 mRNA levels in UC and IBS groups were evidently higher than that in the control group,while patient in UC group had the highest level.And the levels were obviously higher in HBD-2 positive expression rate and HBD-2 expression intensity (2+,3+)in colonic mucosa than that in other two groups. Conclusion HBD-2 plays an important role in the development and progression of UC.