Objective To investigate the clinical significance of pre-operative ancl intra-operative insulinomas localization, and improve the diagnostic accuracy. Methods 75 patients with suspected insulinomas who were treated surgically were enrolled; all the patients had pathological evidence of insulinomas. The data of pre-operative ultrasound, CT, MRI and intra-operative ultrasound and surgical palpation were collected and analyzed. Results The sensitivity of localization procedures was as follows: ultrasonography 30.7% ( 23/75 ), CT 40.0% (24/60) , MRI 45.4% ( 22/48 ) , while surgical palpation was 80.4% , intra-operative ultrasound 96.4%. The accuracy of intra-operative procedures was higher than that of pre-operative procedures. Conclusions It was difficult to accurately localize insulinomas before operation, but intra-operative palpation and iutra-operative US was easy to perform and highly accurate. Therefore, too much emphasis should not be placed on pre-operative imaging tests.