In the current study, knowledge contribution in open web-based encyclopedia is conceptualized as a group-referent intentional social action, and we-intention, which reflects one's perception of the group acting as a unit, has been employed. The motivation of this study thus is to better understand antecedents and consequences of contribution I-intention and we-intention in open web-based encyclopedia. A research model was developed and empirically examined with 202 knowledge contributors in two most famous wiki communities in Mainland China. The results demonstrated that personal outcome expectations exert significant effects on both intentions. Joint commitment, mutual agreement and community-related outcome expectations are significantly related to we-intention to contribute, but not related to I-intention. In addition, we-intention has a statistically significant positive effect on contribution behavior. However, I-intention negatively relates to contribution behavior. We believe this study will serve as a starting point for furthering our limited understanding of the intentional social action in knowledge management research.