Abstract: Nowadays, China's traceability system of aquatic products quality has problems such as non-unified construction standards, uncomplete monitoring for the breeding process, lack of supervision in some circulation links, and tampering with tracing data. In order to solve the above problems, this paper proposes the introduction of blockchain technology into the existing system, expounds the decentralization, autonomy, safety, and reliability of the blockchain, and establishes the traceability system of aquatic products quality based on blockchain. The overall architecture design and hierarchical model of this system are proposed, which breaks the linear data transmission mode of the traditional traceability system and realizes the decentralized information record of aquatic products in the whole supply chain of breeding, circulation and sales. The new system thus enhances the security and transparency of the data information in the whole industry chain. The blockchain-based traceability system of aquatic products quality can be divided into five nodes:aquaculture enterprises, transportation enterprises, sales platforms, government supervision and consumers. The input of quality and safety data can be realized by Internet of Things technology. The data are further blocked and stored through the data layer, network layer, consensus layer, contract layer, application layer and presentation layer, providing services of traceable information for government and consumers. The blockchain-based traceability system for aquatic products quality will make the storage and sharing of traceable data more rapid and transparent, improve the safety and credit ecosystem of the aquatic products supply chain, and promote the rapid development of China's traceability system of aquatic products quality.