Objective To explore the diagnosis and treatment value of narrow-band imaging (NBI) combined with endoscopic ultrasound (EUS) in the ampullary tumors. Methods 21 patients with imaging or endoscopic examination of suspected ampullary lesions were enrolled in this study. All patients underwent NBI and EUS, and 20 patients underwent preoperative biopsy. We predicted ampullary tumor type through preoperative examination, then chose a appropriate surgical method. The resected specimens were subjected to histopathological examination to confirm the final diagnosis. Results The sensitivity of NBI combined with EUS in the diagnosis of ampullary malignancies was 94.12%, specificity was 100%, accuracy was 95.24%, positive predictive value was 100%, and negative predictive value was 80%. The sensitivity of preoperative biopsy for ampullary carcinoma was 41.18%, specificity was 100%, accuracy was 50%, positive predictive value was 100%, and negative predictive value was 23.08%. The accuracy of NBI combined with EUS in diagnosing ampullary malignant tumor was significantly higher compared to preoperative biopsy (P < 0.05). Conclusion NBI combined with EUS examination can more accurately evaluate the benign and malignant tumor of ampullary tumor before operation. It has obvious advantages over preoperative biopsy, and can better guide the choice of surgical methods.