To address the problems of unclear data ownership and security in data transaction scenarios, a decentralized data transaction method and platform based on Ethereum + IPFS are proposed in this paper. The proposed method first performs similar calculations on text using natural language processing technology to realize data rights, then build a transaction body-centered data encryption; finally execute a decryption process through smart contracts to avoid malicious transaction behavior. The designed data-trading platform consists of three parts: customer front-end, back-end, and database. The database adopts the Ethereum and interplanetary file system. Experiments show that the designed platform can solve the problems of unclear data ownership and security in the process of data transactions, reduce data transaction costs, and provide safe and reliable data transaction services for buyers and sellers.