By improvement of Zheng's authenticated key agreement protocol, an identity sign-cryptic technique-based authenticated key agreement protocol is proposed. This protocol has the advantage of sign-cryptic technique and achieves the two functions of authentication and encryption in a single logical step. Therefore, it is of high efficiency. Moreover, due to using ID-based public key system, the expense of building and managing public key infrastructure is decreased and the users need not store or transfer public keys and certificate. And again, in our proposed protocol the bilinear pairing on elliptic curve is employed to reach the equivalent security levels with short length key and small computation cost. As a result, the remarkable properties of our authenticated key agreement protocol are low computation cost, narrow bandwidth requirement, and high security level.