Depression is a state of low mood and aversion to activity that has a negative effect on the patient's thoughts, behavior, feelings, and physical well-being. In the past five years, a significant progress has been made in understanding the mechanism of acupuncture therapy for improving depression. In the present paper, the authors summarize mechanisms of acupuncture for depression from 1) upregulating levels of monoamine neurotransmitters, gamma-aminobutyric acid, 5-HT, receptor binding, and hypothalamic neuropeptide Y, beta-endorphine, and mu-receptor expression, and down-regulating hippocampal glutamate content, etc.; 2) upregulating expression of hippocampal brain-derived neurotrophic factor protein and mRNA and its receptor TrkB, and activating adenyl cyclase-cAMP-PKA-CREB signaling pathway; 3) increasing hippocampal growth-associated protein 43 level and suppressing hippocampal c-Jun N-terminal kinase activation and cellular apoptosis; 4) upregulating expression of glial fibrillary acidic protein (activating glia cells); 5) regulating activities of hypothalamus-pituitary-adrenal axis and hypothalamus-pituitary-sex gland axis; 6) down-regulating serum IL-1beta, IL-6, and tumor necrosis factor-alpha levels. Moreover, the authors also put forward some suggestions about the further research on the mechanisms of acupuncture intervention for depression in the future.