With the development of the computer technology, new ways of model making become an alternative for the representation of the design ideas. In this paper, we present a new design platform based on the mobile augmented reality technology for a co-design situation. A marker-based mobile augmented reality platform for the early phase of the co-design process is presented. A pilot study is conducted and the data is analyzed with the protocol analysis method. In the paper we provide some insights of the impact of the employment of the mobile augmented reality technology in the co-design situation.