In this paper, a delegate contract signing solution is proposed to eliminate the potential risk of contract fraud caused by information and interest asymmetry. By utilizing the functional properties of the Ethereum blockchain and smart contracts, a delegate contract signing mechanism is established. By running the mechanism, the delegate contract signing information is received and processed, and the information is broadcast to the blockchain network nodes. By designing the algorithms of "requesting contract signing", "successful contract signing" and "contract fraud dispute resolution", the delegate contract signing is realized. By proposing algorithms and their calling processes, the smart contracts are completed. Finally, the smart contracts based on the solution are tested and verified. The source code of the smart contracts has been published on GitHub.