The present invention relates to a secure entry method of a radio-frequency identification (RFID) secure entry system including a tag, a reader, a detector, a remote controller, and a locker. According to the present invention, since different data is exchanged all the time using a pre-shared encryption/decryption algorithm to transmit/receive the same data, even when reverse detection occurs from outside, accurate detection may not be easy. Furthermore, since a frequency for data transmission is randomly allocated within a pre-defined frequency list, reverse detection and jamming during communication may be prevented.