This study aimed to explore the dynamic changes of regional brain activity in adolescent with Internet Gaming Disorder (IGD) based on the analysis of dynamic low-frequency amplitude. Methods: Forty-four patients with IGD and 50 age-, sex-, and education-matched healthy controls (HC group) were recruited for resting state magnetic resonance imaging analysis of their regional brain activities. The collected imaging data was analyzed using two independent-sample t-test in which the MATLAB software was used to extract dynamic amplitude of low-frequency fluctuation (dALFF) values of abnormal active brain regions. Person correlation analysis were used to analyze the Internet Addiction Test (IAT) and the SCL-90 scores. Finally, IAT scores, factor scores in the SCL-90 scale and dALFF values of abnormal brain regions in the IGD group were analyzed for moderating effects using the process 4.1 plug-in of the SPSS26 statistical software. p < 0.05 suggests the existence of regulatory effects. Results: IGD group exhibited alterations in the local dynamic activity of signals in several brain regions, compared to HC group. Reduced dALFF values were mainly found in the inferior temporal gyrus, precuneus, posterior cerebellum lobe, and cerebellum vermis regions. The results of dynamic low-frequency amplitude analysis showed a negative correlation between left precuneus dALFF values and IAT scores in the IGD group (r=-0.403, p = 0.008). The results of the correlation analysis with the clinical scale indicated that the dALFF values in the left posterior cerebellum lobe (cerebellum region VI) were negatively correlated with the interpersonal sensitivity factor score (r=-0.314, p = 0.034) and depression factor score (r=-0.342, p = 0.033) in the SCL-90 scale. Conclusions: IGD in adolescents may have an impact on their mental health, and the severity of Internet gaming disorder may play a moderating role between the posterior cerebellum lobe and the mental health status of adolescent Internet addicts, which may provide some useful information in the future to explain clinical phenomena such as Internet addicts with different degrees of emotional problems.