Social cognitive theory indicates that social behavior of participants will change as they interact with others. Interaction in different social environment also results different change degree. The purpose of this study is to identify the social behavior of children during games play in a cooperative and competitive setting. A game named Strike up was developed for the study. The objective of the game is to advance arithmetic practice through five card number calculations and strategies. In order to realize the initiative behavior and change behavior during the game, participants' dialogues were video-taped and its content was later analyzed and interpreted by triangulation. The results of this study suggest that most players tended to express more egalitarian behavior than altruistic, dominating, or individualistic behavior at the beginning. Whereas, female players were more willing to mutually help each other. As playing time going and close to the goal, both boys and girls have more willingness to altruistic play. This implies this type of highly cooperation/ competition game will be a useful tool for children to experience egalitarian and altruistic behaviors.