Understanding what drives user loyalty is a central theme in the research fields of open design community (ODC) and sustained innovation. Drawing on theories of network externalities and expectation disconfirmation, this paper develops a theoretical model reflecting the effect of determinants on user loyalty. The model is tested utilizing survey data amassed from 389 users of a typical ODC, Xiaomi Corporation’s forum, in China. The major findings of our work as follows: First, satisfaction plays the most important role in explaining the user loyalty to ODCs, and disconfirmation of fan care is the most critical factor influencing user satisfaction. Second, the perceived network size exerts negative impact on user loyalty to an ODC. Third, impacts of different factors on user loyalty vary due to gender difference. This research advanced the knowledge in Open Design by demonstrating the antecedents of participant’s loyalty towards ODC, and highlighting the motivations of individual’s open design participation behavior.