The unprecedented Chinese urbanization leads to massive government-funded construction projects. In most cities, a special project management mode called “Agent Construction Model (ACM)” has been adopted to manage and govern these projects under the same umbrella of administrative standards. The ACM integrates all available government resources to complete the urbanization projects but meanwhile it faces great challenges from overwhelming complex information and information processing. This study presents the development of a city-level multi-project management information system to decompose the information processing complexity in the context of ACM management mode. The complex adaptive system and two specific development techniques—adaptive project framework and modularized functional design method—are introduced for the system development. The system was validated at a typical urbanization city in Changchun, China. This research complements the existing project information system by adopting complexity design principles and it also provides practical value for managing large-scale urbanization projects.