Objective To discuss the differences in local spontaneous brain activity among patients with depressive disorder， major depressive episode with mixed feature （MMF）， bipolar disorder with mixed feature （BMF） and bipolar disorder （BD） by amplitude of low-frequency fluctuation. Methods From June to December 2021， resting state functional magnetic resonance imaging data and general information were collected from 20 patients with depression， 15 patients with MMF， 20 patients with BMF， and 25 patients with bipolar disorder who met DSM-5 diagnostic criteria and attended the outpatient clinic of Beijing Anding Hospital， Capital Medical University. 40 healthy people matched with each group in terms of gender and age were recruited as healthy controls during the same period. After image data preprocessing， individual ALFF maps were calculated， and differences in local spontaneous brain activity were explored using one-way ANOVA and post hoc tests. Results The results of one-way ANOVA show that patients with depressive disorder， MMF， BMF， and BD exhibited significant difference of ALFF in the left inferior temporal gyrus ［cluster size k=372， P ＜ 0.001， Family Wise Error （FWE） corrected］， left raphe nuclei （k=271，P ＜ 0.001， FWE corrected）， right anterior cingulum （k=193， P＜ 0.001， FWE corrected）， right middle temporal gyrus （k=149， P＜ 0.001， FWE corrected）， right superior media frontal gyrus （k=117， P＜ 0.001， FWE corrected）， right cerebellum crus （k=68， P=0.009， FWE corrected）， right inferior temporal gyrus （k=63， P=0.014， FWE corrected）， and left middle temporal （k=49， P=0.048， FWE corrected）. The post hoc test results showed that the ALFF values of the left inferior temporal gyrus in patients with bipolar disorder and BMF were higher than those in patients with depression， while the ALFF values of the right cerebellum in patients with MMF， bipolar disorder and BMF were lower than those in patients with depression， and the differences were statistically significant （P＜ 0.01）. The left raphe nuclei ALFF value of BMF patients was lower than that of MMF and depression patients （P＜0.05）. Conclusions In patients with affective disorder spectrum， local spontaneous brain activity in frontal lobe， temporal lobe， cerebellum， raphe nuclei and other brain regions is abnormal， but in BMF patients， compared with MMF patients， local spontaneous brain activity in raphe nuclei is weak.