Positive affect is not only an important component of well-being, but also has positive impact on individual’s physical health, cognition, and social relationship. Our project aimed at exploring the impact of positive affect on Chinese high school students’ academic engagement, and examining whether group intervention can increase their positive affect. In Study 1 we investigated the moderation effect of self-control on the relationship between positive affect and academic engagement in 277 high school students. In Study 2 we conducted group intervention based on positive psychology and cognitive behavioral therapy to explore its impact on 24 10th grade students. We found that, (1) Contentment and fulfillment positively predicted academic engagement. Thinking control positively predicted academic engagement. Behavioral control negatively moderated the relationship between positive affect and academic engagement. (2) The pre-test score were not differed, while post-test score of positive affect significantly differed between these two groups. Our results indicated positive affect and thinking control affect academic engagement, and as behavioral control score gets higher, the predicting power of positive affect weakens. Group intervention based on positive psychology and cognitive behavioral therapy increases adolescents’ positive affect. Our study has significance on students’ cognition development, academic engagement and mental health.