Objective To study the value of preoperative MRI in diagnosing and typing anal fistula.Methods The clinical data and MRI findings of 36 operated patients with anal fistula were analyzed retrospectively, and compared with pathological results of the operations, the manifestation and application value of MRI in anal fistula were summarized.Results 36 cases of anal fistula showed 42 internal openings,45 primary tracts,15 small tracts,42 external openings,16 abscesses.Compared with surgical results, the accuracy of MRI was 90.5%(38/42) for internal openings,80%(12/15) for small tracts,100% for primary tracts, external openings and abscesses respectively.According to the Parks type, the coincidence of MRI classification was 88.9%(32/36).Conclusion MRI can accurately display the position of the internal and external openings, the number and form of the tracts, and type about anal fistula.