Due to the high requirements for security and confidentiality of contract data and the potential security risks in the Internet, the current contract management system cannot fully utilize the advantages of the Internet to achieve online operations. Identity authentication and contract signing are technical difficulties in online operations. In order to realize the contract management system running on the public network server, and complete the company identity authentication and contract signing online, this study designs and implements a contract management system based on private chain technology. First, this study proposes the design concept of the company’s digital authentication center, which is used to manage the company’s digital information and participate in the company’s identity authentication; then it designs the implementation scheme of the contract management system and private chain system, and finally introduces the technical points in the implementation of the system. The analysis of experimental results shows that the management system can realize all the processes of contract management online, which improves the efficiency of contract management.