Abstract: The security of Wang-Li-Zhou's proxy blind multi-signature based on Elliptic Curve Cryptography is analyzed,and it is shown that proxy signer can confirm the relationship between his signing action and the signed message using the reserved blind signature information and signature information publicized by message owner.Then the identity of message owner can be tracked,that is to say their scheme dissatisfies non-trail.An improved proxy blind multi-signature is proposed,and cryptanalysis shows that it satisfies non-trail and other security properties.