In order to solve the problem of information island between the block chain of each enterprise link in the existing aquatic products supply chain and realize the cross-chain transaction between enterprises, the architecture and model of aquatic products transaction based on the cross-chain technology of block chain were proposed. The architecture of cross-chain aquatic product trading system was established by combining the trading business in aquatic product supply chain, and cross-chain technology was used to modularize the trading requirements and cross-chain functions to build the aquatic product trading model based on cross-chain technology. Then the cross-chain trading process was designed based on this model to realize the interaction between each functional module. Finally, the corresponding smart contract was designed to complete the cross-chain transaction between enterprises in the aquatic products supply chain. The Hyperledger Fabric platform was applied to build the cross-chain transaction model for aquatic products. The results of the system performance test showed that the average success rate of cross-chain transactions was stable at about 99%, and the average delay rate of transactions was about 0.2s. The proposed cross-chain aquatic product transaction model not only met the demand of existing aquatic product supply chain in on-chain transactions, but also ensured the success rate and security of cross-chain transactions.