Computer technology provides technical guarantee for legal decision-making and digital governance, and also brings related legal and ethical topics. The functional requirements of the data legal decision support system are examined in this paper, and the architecture design is completed by adopting the MVC pattern and three-layer B/S architecture. Based on this basis, the network topology and database design of the system have been completed. The analysis shows that there is a significant positive correlation (β=0.173, 0.127, 0.378) between the frequency of use, the length of use, the position of the user and the quality of decision-making of the legal decision-making support system and that the speed of approving a certain type of contract of Company M using this system has been increased by as much as 80.67%, and that litigation costs of 10.8 million yuan are saved after the system partially replaces the external lawyers. In addition, users have a positive evaluation of the system’s professionalism. The legal and ethical considerations related to this decision support system in digital governance are examined in this paper.