Objective To compare the differences in default mode network （DMN） and affective network （AN） between adolescents with depressive disorder and a healthy control group in a resting state based on independent component analysis （ICA）. Methods From October 2022 to July 2023， 47 adolescents with depressive disorder admitted to the outpatient and inpatient departments of Suzhou Guangji Hospital were selected as adolescent depression group， while 35 healthy controls matched for gender， age， and education were selected as the healthy control group during the same period. Two groups of subjects underwent resting state functional magnetic resonance imaging （rs-fMRI） scans. ICA was used to extract the DMN and AN of two groups of subjects， compare the intra network differences between the two groups. Pearson correlation was used to analyze the correlation between differential brain regions and Patient Health Questionnaire-9 （PHQ-9） score and disease course in adolescents with depressive disorder. Results Compared with healthy control group， the left superior frontal gyrus， left angular gyrus， left posterior cingulate gyrus， left inferior parietal lobule， and right superior temporal gyrus were significantly activated in DMN of adolescent depression group， and the left anterior cingulate gyrus， left temporal pole superior temporal gyrus， left anterior cingulate cortex， and right insula in AN were significantly activated （FWE correction， P＜ 0.05， voxel size ＞ 25）. The left anterior cingulate gyrus in the adolescent depression group was positively correlated with PHQ-9 score （r=0.327， P=0.025）， the left anterior cingulate gyrus was positively correlated with the patient's disease course （r=0.394， P=0.006）， and the right superior temporal gyrus was positively correlated with the patient's disease course （r=0.297， P=0.043）， with statistically significant differences. Conclusions Adolescents with depressive disorder exhibit abnormal activation of DMN and AN brain regions in a resting state， and some brain regions are significantly correlated with scale scores and disease course， suggesting that it may be related to cognitive function changes such as emotional processing and memory processing in adolescents with depressive disorder.