With the development of e-business market, radio frequency identification (RFID) technology is becoming more and more importance. It is often used to identify object because it can work without manual intervention. Several organizations including EPC global and ISO have been working on the standard of RFID all the time in order to promote it using low-cost tags. In particular, the EPC Class-1 Generation-2 standard was accepted as an international standard by ISO/IEC. However, this standard exists some security vulnerabilities. To resolve these vulnerabilities, some protocols conforming to EPC Class 1 Generation 2 was proposed. In this paper, we show the weaknesses which exist in RFID system’s security protocols conforming to EPC Class-1 Generation-2 and submit a new security protocol suitable to the standard, then validate the whole security performance of the new protocol. The safety performance of the new protocol and existing protocols are also compared in this paper .The result shows that the the new protocol could be used in the low-cost tag because of its high security and low communication complexity.