Objective: Based on the dual-factor model of mental health, this study aims to explore the effects of acceptance and commitment therapy on the mental health of high school students. Methods: During Oct. to Nov. 2017, General Health Questionnaire12(GHQ-12) and Depression Anxiety and Stress Scale21(DASS-21) was administered among 543 high school students from a middle school in Nanchang. According to the inclusion and exclusion criteria, 20 high school students were screened and were randomly assigned to the intervention group and control group, respectively. The intervention group received one intervention (1.5 h) per week for 8 weeks. The control group did not receive the intervention. Pre-and post-intervention assessment were conducted using the Acceptance and Action Questionnaire-2nd Edition (AAQ-II), the Cognitive Fusion Questionnaire-Fusion (CFQ-F), the Satisfaction With Life Scale (SWLS), the Positive Affect Scale (PAS), the GHQ-12, and the DASS-21. Results: After intervention, the post-test scores of AAQ-II, CFQ-F, GHQ-12, and DASS-21 in the intervention group significantly decreased (t=2.91, 2.47, 4.91, 4.42, P<0.05) and the post-test score on PAS significantly increased (t=-5.27, P<0.01). There were no statistical changes in AAQ-II, CFQ-F, GHQ-12, and DASS-21 scores in the control group after intervention (t=-1.25, -0.09, -0.61, -0.69, -0.81, P>0.05). Conclusion Acceptance and commitment therapy can effectively improve the psychological flexibility and positive emotions, as well as alleviate general psychological distress and negative emotions, and promote the improvement of mental health of high school students.