Knowledge acquires collaboration in producing innovations. Diversities, i.e. expertise, backgrounds, and also resources, are essential for the collaboration. Hence, the activities of sharing, transferring and also exchanging resources between diverse participants become vital in realizing the innovation. This circumstance is recently found in the design process of buildings. The development of building's requirements leads to complexities in its design. Collaboration is fundamentally needed to attain best design. Knowledge Management found to be essential factor for the collaboration practices. The practices are also known as Group Decision. This study intends to discover issues, roles, and impacts of Knowledge Management towards successful Group Decision in design process. Literature review is used to build the conceptual model, and the conceptual model is empirically confirmed to designers and consultants of high-rise buildings. The empirical data is analyzed by using correlation and regression analysis. The results of this study are conceptual and empirical model of Knowledge Management towards successful Group Decision. Both models can be used to support the development of Computer Supported Collaborative Design in supporting the achievement of successful Group Decision works.