This study investigated online gamers of World of Warcraft, especially their knowledge of teamwork, team building, and shared mental models (Cannon-Bowers & Salas, 1990, 1993). We analyzed the contents of their shared mental models and examine whether it is possible to put coherent contents into several categories. We recruit 7 members of a raid Karazhan team. They were acknowledged as core players and leaders in a large guild of Taiwan. Then one-on-one interview was conducted and protocols were transcribed. The result showed that: (1) Core gamers had enriched facts, relational, dynamic knowledge about games and problem solving (gaming) skills. The team we chose was very particular in their stable team structure. (2) These core gamers named their own team as "fun seeking group"; comparatively others were coined as the "performance striving group." Game teams could be described as doing "hard work for hard fun." All gamers regarded their playfulness atmosphere is very precious and very rare among teams. This scarce feature in turn affected the team structure and functions. Finally, we found the shared mental model is adequate to describe core gamers' knowledge with some modifications and we limited the scope to examine the "knowledge about group", the "knowledge about team mate" and the "knowledge about avatar."