The rapid development of Internet has promoted the extensive application of e-commerce. The stolen identity of users, and the electronic contract tampering have seriously affected the fairness and security of online electronic transactions. For the main participant of the transaction, it is a primary and pivotal problem to solve how to confirm the identity of the other party is genuine and credible and how to confirm the electronic contract is sent by the other party with authenticity, credibility, and non-repudiation. In order to ensure the uniqueness of the user identity, transmission data integrity and non-tampering, the contract process traceability, this study combines the user authentication, electronic contract encryption transmission, notary office to participate in notarization and other methods to design electronic contract service platform, which achieves fairness in the use of the platform.