Objective To study the application yalue of MSCT in complex anal fistula.Methods The data on 35 patients with complex anal fistula,who received MSCT examination before the operation in our hospital,were retrospectively analyzed.The raw data were processed by use of the technologies of multi-plane reconstruction (MPR),volume reconstruction (VR) and surface reconstruction and the results were compared with the operation results in order to analyze the clinical diagnostic accuracy of MSCT.Results From MSCT examination detected lower complex anal fistula in 16 cases and higher complex anal fistula in 19 cases.The accuracy of MSCT in the classification of complex anal fistula was 100%,and the accuracy,sensitivity and specificity in positioning the internal stoma of complex anal fistula was 92.45%,95.17% and 68.74% respectively.The detection rate of the branch of complex anal fistula was 90.79%.Conclusion MSCT has high accuracy in the diagnosis of complex anal fistula and has important guiding significance in development of operation plan.