Proxy ring signature schemes have been shown to be useful in various applications, such as electronic polling, electronic payment, etc. In this paper, we point out that Langs scheme is unreasonable and propose an improved Identity-based proxy ring scheme from bilinear pairings which is reasonable and overcomes the deficiencies of Langs scheme. Our scheme can prevent the original signer from generating the proxy ring signature, thus the profits of the proxy signer are guaranteed. In addition, our scheme satisfies all the security requirements of proxy ring signature, I.e. Signer-ambiguity, non-forgeability, verification, non-deniability and distinguishability. As compared with Zhangs scheme, our scheme is a computational efficiency improvement for signature verification because the computational cost of bilinear pairings required is reduced from O(n) to O(1).