Maintaining authenticity for multicast communication is inherently more complex than for unicast, which dues to the dynamic group and unreliable delivery. In the implementation of multicast authentication, the major obstacles lie on the lower signature rate and larger signature size overhead. To solve this problem, by using a new authentication technique called authentication matrix, a new signature scheme is proposed for large and dynamic multicast groups that can be used on the unreliable delivery network. Comparing with the existing schemes, in this scheme, the signature size overhead is much smaller and the signature rate is much higher, and it can provide the non-repudiation serve. It should have application in many practical fields such as multimedia data transmission, live multi-party conferencing and long-distance education.