This paper analyzes the security of a group signature scheme based on Chinese Remainder Theorem proposed by Chen-ZW recently.The security of Chen-ZW's scheme relies on the assumption of integer factorization

but it is computable to factor the large integer in the scheme because all the group members share a same RSA modulus n.Therefore

the security assumption is unsuitable for the scheme

and the advantage of the scheme is virtually nonexistent.The paper also gives a modified scheme

which elaborately eliminates the defect of the original scheme and improves the efficiency of the protocol.