Objective:To explore the application value of three-dimensional high-resolution anorectal manometry(3D-HRAM)model in the diagnosis and localization of anal sphincter injury after surgery for complex anal fistula.Methods:A prospective study was con-ducted on 92 patients who had undergone surgery for complex anal fistula in the Department of Coloproctology of The People's Hospi-tal Affiliated to Fujian University of Traditional Chinese Medicine from January 2023 to January 2024.The study was conducted in two stages.In the first stage,92 patients underwent 3D-HRAM and endoanal ultrasonography(EAUS)to examine the sphincter,and the data were compared with intraoperative records to evaluate the diagnostic efficiency and localization accuracy of 3D-HRAM and EAUS.In the second stage,92 patients who had been examined were grouped according to the presence or absence of symptoms of anal dysfunction to further verify the diagnostic and localization values of 3D-HRAM and EAUS for postoperative compensated/decompen-sated sphincter injury.Results:Among 92 patients,41 and 57 patients were diagnosed with sphincter injury through 3D-HRAM and EAUS,with a sensitivity of 61.19%and 85.07%,a specificity of 88%and 76%,an area under the curve of 0.739 and 0.813 calcu-lated by plotting the receiver operating characteristic curve,and a localization accuracy of 44.77%and 71.64%,respectively,showing significant differences between 3D-HRAM and EAUS(P=0.002),indicating that 3D-HRAM had lower diagnostic efficiency and local-ization accuracy than EAUS for anal sphincter injury after surgery for complex anal fistula.After grouping by symptoms,the diagnostic efficiency and localization accuracy of 3D-HRAM for symptomatic sphincter injury(decompensated)were significantly better than those for asymptomatic sphincter injury,and were similar to those of EAUS(P=0.763).Conclusion:The application advantage of 3D-HRAM lies in the diagnosis and localization of decompensated anal sphincter injury after surgery for complex anal fistula,which provides effective technical support for the study of anal defecation control mechanisms and injury compensation mechanisms.