Blockchain technology, characterized by decentralization, transparency, and immutability, has been widely applied in areas such as supply chain tracking, medical data management, and the Internet of Things. However, single blockchain systems suffer from limitations in performance, scalability, and cross-chain interoperability, giving rise to the issue of “blockchain silos.” To address the challenges of data and asset circulation among heterogeneous blockchain networks, both academia and industry have proposed multi-blockchain architectures. In this paper, we categorize current multi-blockchain systems from a network topology perspective into four types: parallel architecture, hierarchical architecture, hybrid architecture, and multi-blockchain networks. We systematically review the main cross-chain technologies, including main/side chains, relay chains, bridge nodes, cross-chain smart contracts, and hash time-locks. Furthermore, we summarize representative applications such as data exchange, transaction validation, medical data management, supply chain traceability, and IoT management. Finally, we also identify challenges, like cross-chain security, consensus compatibility, resource overhead, and decentralized coordination mechanisms. Meanwhile, we discuss future works, including lightweight relay networks, zero-knowledge proofs, modular chain architectures, and reinforcement learning-based scheduling. Through multi-dimensional technical analysis, we provide a systematic survey for the theoretical study and applications of multi-blockchain, facilitating the usage of multi-blockchain in the digital economy and trusted collaboration contexts.
Wu et al. (2026) studied this question.