Objective: To explore the effects of a classroom based transdiagnostic preventive intervention program for emotional disorders on depressive and anxiety symptoms, and resilience among junior high school students, so as to provide reference for promoting adolescent mental health. Methods: From October to December 2023, 72 students from a junior high school in Beijing were recruited as research subjects and divided into an intervention group ( n =36) and a control group ( n =36). The intervention group participated in 8 sessions (40 mins per session) of transdiagnostic prevention intervention course for emotional disorders; the control group students participated in research based learning lessons or class meetings. Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and Resilience Scale-8 (RS-8) were used to evaluate junior high school students. The Wilcoxon signed rank test was used to compare the differences in depressive and anxiety symptoms, and resilience scores between the intervention group and the control group before and after the intervention. PROCESS macro was used to test the mediating effect. Results: There were no statistically significant differences in the scores of depressive and anxiety symptoms, and resilience before and after intervention in the intervention group ( Z =-1.07, 0.07, 1.43, all P >0.05). In the control group, the depressive symptoms score was higher after the intervention than before, and the resilience score was lower than before the intervention ( Z = 2.23 , -2.53, both P <0.05). After intervention, the depressive symptoms score in the intervention group was lower than that in the control group, and the resilience score in the intervention group was higher than that in the control group ( Z =-2.09, 3.33, both P < 0.05). The increase in the scores of resilience played a complete mediating role between the intervention and depressive symptoms, with the mediating effect value being -0.98 (95% CI =-2.47 to -0.11), accounting for 30.98% of the total effect. Conclusion Transdiagnostic preventive intervention program for emotional disorders based on classroom could prevent the deterioration of depressive symptom in junior high school students, and maintaining the level of resilience is an important factor for the intervention effect.