Recently, the amount of cloud service usage is increasing explosively. Specially, request of cloud service that use do computer or mobile communication device is very high in university or book related organ. However, level of security service is very low that against of amounts that using request in BRS (book retrieval system). Therefore, we wish to give other access grade in user in this research and propose easy and safe authentication method (ESAM: Easy and Secure Authentication Method using PMI) to book retrieval system so that access control and authentication about user may be available. Our proposed method based on PMI’s attributes certificate technique. And our scheme can solve various security problems on existent book retrieval system. After next study, we will investigate our propose method against of existent way and improve our method is more good.