Users' signing order is an important factor in?multisignature schemes. In fact the signing order often reflects signer's rank in a signing group. So far, many multisignature schemes, called structured schemes, that provide have been proposed. However, there are not many structured multisignature schemes utilizing an algebraic structure of underlying algebraic operation. In this paper, we adopt a non-commutative ring homomorphism for constructing a structured multisignature scheme and study the security of the constructed scheme under the discrete logarithm assumption.