Objective To establish simple and accurate evaluation standard of the access preparation of molar and verify its reliability. Methods 9 undergraduate students who had entered clinical practice for one month prepared access of molars in vitro. 10 dentists specialized on endodontics for 5 to over 15 years evaluated the molars according to the evaluation standard. Intraclass correlation coefficient of the results was analyzed by SPSS Statistics. Results The intraclass correlation co-efficient on the evaluation of 10 endodontists was 0.739 (P=0.000)

which had statistical significance. The result was between 0.61 and 0.80 which meant the quality of reliability was moderate. It illustrated that the inter-observer reliability was medium. Conclusions The evaluation standard of this study has good reliability and is not influenced by the clinical experience of observers. And it is worth the further exploration and extension.