Abstract: Certificateless public key cryptosystem，one of the hot topics in current research，overcomes the problem of the certificate management in the traditional certificate-based public key cryptosystem and the inherent key escrow problem in the identity-based public key cryptosystem.The certificateless proxy blind signature scheme，which has been proposed recently by Chen Hu etc.，is analyzed and their scheme turns out to be severely insecure.That is，a dishonest user can recover the proxy private key of the proxy signer；then he can do what the proxy signer can do.Finally，to conquer this attack，a comprehensive and improved scheme is proposed，whose security is based on the CDHP．