Authentication is a security requirement with high priority in many multicast applications. One-Time Signature (OTS) is a promising solution to the multicast authentication problem. However, it often suffers from large signature sizes and frequent distributions of the public keys. In this paper, we propose a lightweight OTS scheme to combat these drawbacks. Our approach integrates the signature amortization technique and one-way hash chains, which markedly reduce the average communication overhead and relax the key renewal requirements. We also introduce a partial key renewal mechanism to provide a convenient means of renewing key pairs. In addition, our scheme is highly secure against signature forge and is resistant to packet losses. Numerical results show that our scheme achieves better performance than a former scheme under DoS attacks.