It has always been a critical issue to find efficient methods for fast revocation of a user?s identity in traditional ID-based cryptosystems. In this paper, we present an efficient mediated certificateless public-key encryption scheme (MCL-PKE for short) without using bilinear pairing. The proposed MCL-PKE scheme solves the inherent key escrow problem of traditional identity-based cryptosystems and provides instantaneous revocation property simultaneously. In addition, our scheme is IND-CCA secure against two types of adversaries in random oracle based on the hardness of the Computational Diffie-Hellman Problem.