RFID system is facing the serious problems of private security, which mainly consists of the leakage of tag sensitive information, tracking and monitoring spitefully the carrier of mobile tag. This paper constructs a coordination protection mechanism of tag private information by a variety of reader-writer, which solves the two questions mentioned above. Firstly, a trust-security mechanism used to ensure that the readers in system are trustful. Next, via intercommunication of the readers, the secret key, which is produced by the tag-charged reader, is divided and distributed to the various readers in system. The test result shows that attackers cannot gain the shared secret key from various readers, and he/she could only read an encoded data, thus the security of private information in tag is guaranteed. Additionally, a set of readers use coordination-protection mechanism, which is an efficient way to improve the expandability of the system.