Objective To evaluate the diagnostic ability of differentiating pathological nature of the Japan NBI Expert Team (JNET) classification. Methods 418 lessions were retrospectively diagnosed by JNET classification through observing the microvessle and surface structure under magnifying endoscopy with NBI by two doctors with no experence of using magnifying endoscopy. The results were then compared with actual histologic findings.Results With ME-NBI JNET classification the sensitivity, specificity, positive predictive value(PPV), negative predictive value(NPV) and accuracy which for differentiating neoplastic change was 98.2%,77.8%,98.5%,75%,96.9% respectively,which for diagnosing cancer which includes High grade intraepithelial neoplasiae/Intramucosal carcinoma and submucosal carcinoma was 66.7%,87.6%,66.1%,87.9%,82.1% respectively,and which for predicting submucosal deep invasive cancer was 34.8%,100%,100%,96.3,96.4%.The diagnostic accuracy which for cancer was 95.2% in 0-9mm group,85.1% in 10-19mm group , 72.1% in more than 20mm group and which for submucosal deep invasive cancer was 100%,96.3%,94.4%,respectively in each group. Both of them emerged significant difference with P ＜0.05.Otherwise,the shape and location of colorectal lessions have no significant effect on the diagnostic ability of JNET classification. Conclusion JNET classicfication is valuable for doctors with no experence of ME-NBI in diagnosing colorectal lessions afer a short time training.However, for big polyps especially two centimeters or more ,the accurancy of diagnosing cancer need to be improved.