The current study investigated the mediating effect of positive internet game expectancy on the relationship between behavioral activation system and internet game addiction to confirm whether the acquired preparedness model which has been verified in substance addiction field could be applied to internet game addiction field, then tested wether the effect is moderated by game refusal self-efficacy. 349 gamers aged 13 above participated this study. The results showed that the behavioral activation system boosted the positive game expectancy and then increased the risk of internet game addiction, but the effect was buffered by game refusal self-efficacy. Focused on the results, therapeutic suggestions about current study were discussed.