Group-buying is an intriguing e-commerce model that aims to recruit more participants to generate sufficient orders to establish a low-price foundation. It appears to be a good model for both sellers and buyers; however, most online group-buying websites have failed. Many academics believe that reputation-sharing across multiple platforms is the way to solve the industry’s dilemma. RS-Chain is a blockchain-based decentralized reputation-sharing framework, has been proposed in this paper. It is a hybrid blockchain comprising multiple public chains that store transaction ledgers and a consortium chain that stores reputation ledgers. It employs a trusted execution environment as a data verification component. We introduce the framework and describe the reputation operations. For the public chain, we propose proof of reputation (PoR), a new consensus protocol. The comparison experiment demonstrates that the PoR protocol outperforms the proof of work protocol in terms of fairness, orphan blocks, throughput, and latency. RS-Chain is the first reputation-sharing framework based on blockchain technology in the group-buying industry. It could be applied to similar reputation-sensitive industries.