Objective: To evaluate the application value of ductoscopy for diagnosis of pathologic nipple discharge. Methods: The clinical data of 1606 patients with pathologic nipple discharge undergoing ductoscopic examination and resection were retrospectively analyzed. Results: Although the results of the ductoscopy were not entirely consistent with those of the final pathology, there was a relatively high consistency between the two diagnostic methods (Κ=0.828). The sensitivity and specificity of ductoscopic diagnosis was 95.5% and 88.6% respectively, and its consistency rate with pathological diagnosis was 94.0%. Conclusion: Ductoscopy has considerably good sensitivity and specificity in diagnosis of nipple discharge and has a high consistency with the pathology findings, thus it can be used as an important approach for clinical diagnosis of mammary gland disease.