RFID system generally includes three parts: tag, reader and database, where there is the hidden danger between tags and reader through wireless communication. In order to ensure the security of communication information, a bidirectional authentication protocol which is suitable for label and reader is proposed, which can solve the problem of security hidden danger. Bidirectional authentication protocol adopts the mechanism of transmission after message encryption, which makes the attacker eavesdropping information is not clear, thus ensuring the security of information.