Abstract: The security of the proxy blind signature scheme which is proposed by Tan et al is analyzed，and it is found that this scheme can’t satisfy the unforgeability and the unlinkability requirement.This paper presents an improved scheme that can overcome the security problems existing in Tan et al’s scheme.The new scheme improves the signing equations in signing phase.Consequently，its security is equivalent to find a solution to the discrete logarithm problems against the universal forgery attack.Moreover，the receiver’s private key is introduced in extraction phase，which ensures the proxy signer can’t make a linkage between the signature on message and the signature on corresponding blind message.