A necessary problem in public key cryptosystem is how to revoke a user when the user's private key is compromised or the permission is prohibited. There have been many effective solutions in both traditional public key cryptosystem(TPKC) and identity based cryptosystem(IBC). But, in certificateless public key cryptosystem the revocation problem still remains to be efficiently solved. As is known, certificateless cryptosystem is a good substitution for TPKC and IBC since it features no certificate and no key escrow with only a little more computation. So, it is very necessary to design efficient revocation solutions in the certificateless setting. This paper gives a revocable certificateless signature scheme in which the system periodically generates new time keys for all non-revoked users via public channels. Compared with the existing Al-Riyami and Paterson revocation mechanism, our scheme is much better in efficiency. Furthermore, the new scheme can resist signing key exposure with very short signing key. In the CDH assumption, our scheme is UF-CMA provably secure.