Abstract: Innovation activities have transformed from the traditional firm-driven type to the user co-creation type. Open innovation platforms couple the innovation demands of enterprises and the supply of users' innovation ability, and strive to make the source of innovation fully surging. However, the degree of user-engagement is severely insufficient. So, it is important both theoretically and practically to find out how to design an open innovation platform mechanism that can enhance user engagement. We propose that gamification design might facilitate user engagement. Based on the evidence from the world's largest data science open innovation platform, Kaggle, this study explores the impact of reward and coopetition on user engagement behaviors and reaches the following conclusions. (1) The amount of reward money has a positive impact on user engagement; (2) the number of prizes negatively moderates the impact of reward quantity on user engagement; (3) restricting team size negatively moderates the impact of reward quantity on user engagement; and (4) banning team merger in the later stage does not affect user engagement. The current research enriches the theoretical accumulation in the field of innovation management, and provides practical implications for open innovation sponsors and managers to design rewards and organize activities in order to enhance user engagement.

Key words: gamification, open innovation platform, user engagement, reward, coopetition