<p>In resource-constrained Internet of Things (IoT) environments, threshold-based digital signatures have become a key technology due to their decentralized security advantages. However, existing threshold signature schemes primarily face computational inefficiency and insufficient scalability in key management when deployed in IoT environments. To address these problems, this paper proposes a lightweight threshold signature scheme based on Random Grid Secret Sharing (RGSS), which effectively balances the trade-offs among security, efficiency, and scalability in IoT application environments. Specifically, we first design a lightweight signature framework for IoT environments. Second, we generate keys using a random grid-based secret sharing method and introduce random auxiliary values during the signature generation process to enhance the security and reliability of the signing process. Finally, we propose a signature aggregation technique based on XOR operations, combined with an efficient hash verification mechanism, to achieve rapid signature combination and verification, significantly improving signature aggregation efficiency. Experiments and analysis demonstrate that as the number of participants increases from 50 to 400, the computational overhead of our scheme increases only from 0.361 ms to 3.024 ms, while the resource overhead, particularly the memory size during the verification phase, is merely 0.58 KiB, outperforming existing schemes in both computational efficiency and resource overhead.</p>