Objective To investigate serum IL-32 level in patients with ulcerative colitis (UC) and its relationship with the severity of UC. Methods Fifty UC patients (16 mild cases, 20 moderate cases and 14 severe cases) and 30 healthy controls were enrolled in the present study. Peripheral blood of the UC patients and the healthy controls was collected respectively. Total RNA in PBMCs was extracted by TRIzol Reagent. IL-32 mRNA expression level was detected by real-time PCR. IL-32 protein expression level in serum was assayed by ELSIA.Difference in IL-32 expression level between the UC and control groups was compared using student’s t test.Differences in IL-32 expression level among the mild, moderate and severe UC groups were compared using analysis of variance. Results Serum IL-32 expression level of the UC patients was higher than that of the healthy controls both at RNA and protein levels (P < 0.05). Serum IL-32 expression in the severe UC group was statistically higher than that in the moderate and mild UC groups, respectively (P < 0.05). Conclusions Serum IL-32 expression in UC patients is increased. IL-32 might be involved in the pathogenesis of UC.