Abstract: Objective To investigate the effects of FKBP12.6-knockout on colon contraction in mice with dextran sulfate sodium(DSS)-induced colitis and its primary mechanisms. Methods RNA extraction from colonic smooth muscle of both FKBP12.6 knockout (KO) mice and wild-type mice (WT) were prepared for RT-PCR which proved the expression of FKBP12.6 in colonic smooth muscle of wild type mice. The WT mice (aged 8-12 weeks) were randomly divided into control group (n=13) and DSS group(n=13), so did the age and sex-matched littermate KO mice. The four groups were named WT control, WT DSS, KO control and KO DSS. Acute colitis was induced by 3% DSS in the drinking water for 7 days. Then clinical manifestations, weight loss and colon length were compared between two DSS groups. Contractility of colonic SM strips was measured in an organ bath. Ca²⁺ handling protein including IP3R1, PLB and BKCa expression was determined by western blotting. Results The lengths of colon and the frequency of colonic contraction in the two control groups showed no significant difference. And there was no significant difference in clinical manifestations, weight loss and colon length between WT DSS group and KO DSS group. While, the frequencies of spontaneous contractions of smooth muscle strips in WT DSS group were significantly higher when compared with KO DSS group(15.22±2.90) times in 5 min vs (2.10±0.38) times in 5 min, n=9, P< 0.01, and so did the WT DSS group compared with WT controls (15.22±2.90) times in 5 min vs (3.78±1.64) times in 5 min, n=9, P< 0.01. However, it was similar in two KO groups.Western blotting showed that there was no significant difference in IP3R1, PLB and BKCa between WT and KO controls. However, IP3R1 was significantly lower in KO DSS group than that in WT DSS group (0.56±0.14 vs 0.84±0.09, P < 0.05), and BKCaexpression was higher in KO DSS group than that in WT DSS group (0.97±0.14 vs 0.53±0.13, P< 0.05). No significant difference was found in PLB. Conclusion FKBP12.6 knockout has no effect on the clinical manifestations, weight and colon lengths of DSS treated mice. The contraction of colon in KO DSS group is similar to that in WT control group.