Public building is an important component of city and environment and an essential carrier of citizens’ life. With the development of the times, the connections between public buildings and cities, environment, and citizens are becoming increasingly close, and public building itself presents the characteristics of diversification and high integration. The development of digital technology application in the design field provides a new method for achieving the integration of multiple systems in public buildings. By elaborating on the design methodology of three practical projects that I participated in, this paper discusses the innovative application of digital technology in public buildings design and explores a new path for architectural design and construction in the era of human–machine symbiosis. In the three projects, we mainly utilize the three-dimensional digital information model as the carrier of digital collaborative technology, responding to three design questions, respectively: (1) How to generate public buildings closely connected with surrounding buildings and sites under complex terrain conditions, (2) How to coordinate the respective needs of form, structure, and function in the form-finding of long-span buildings, and (3) How to reduce the space occupation through the integration of multi-professional systems.