With the expansion of RFID technology application in diverse fields, the security problems attract more and more attention. In the RFID Security authentication protocols used public-key cryptography, the authentication protocol based on the ECDLP (Elliptic Curve Discrete Logarithm Problem) can solve the clone and reply attacks very well, but there are more or less problems in resisting tracking attacks. In this paper, we present a 'Randomized Key' proposal based on ECDLP and improve EC-RAC (Elliptic Curve Based Randomized Access Control) protocol and Schnorr protocol respectively. Our security analysis shows that the proposed improved protocols can resist tracking attack effectively.