This study aims to investigate the effects of chronic unpredictable mild stress on depressive mood, spontaneous brain activity, and functional connectivity in rats. Behavioral tests were conducted to examine the impact of chronic unpredictable mild stress on depression-like behaviors such as anhedonia and despair in rats. Resting-state fMRI scans were used to detect changes in brain function following stress, and characteristic functional connectivity patterns and brain regions associated with stress were analyzed. The results showed that the chronic unpredictable mild stress model reduced sucrose preference in rats and increased immobility time in the forced swim test, thereby inducing depression-like behaviors characterized by anhedonia and behavioral despair. Resting-state fMRI revealed reduced ALFF values in the nucleus accumbens, thalamus, amygdala, bed nucleus of the stria terminalis, hypothalamus, and other brain regions in this model. ReHo values were significantly reduced not only in the aforementioned brain regions but also in the tegmentum of the midbrain, piriform cortex, prefrontal cortex, and other brain regions. Additionally, functional connectivity analysis revealed widespread reductions.