Abstract：Parkinson's disease（PD）complicated with depression is a neuropsychiatric comorbidity characterized by core motor symptoms of PD complicated with depressive mood disorders. Its pathogenesis mainly involves intestine- brain axis dysfunction，specifically manifested in two core pathological links：intestinal microbiota dysregulation and neurotransmitter disorders. Intestinal microbiota dysregulation promotes abnormal aggregation of α-synuclein，increases intestinal barrier permeability，releases inflammatory factors，damages dopaminergic neurons，and reduces microbial metabolites affecting 5-hydroxytryptamine（5-HT）synthesis. Dopaminergic neuron damage in PD patients leads to dopamine（DA）depletion，dysfunction of 5-HT，norepinephrine（NE），and γ-aminobutyric acid（GABA）systems， as well as reduced brain-derived neurotrophic factors，causing emotional regulation disorders and jointly inducing motor dysfunction and depression-like symptoms. Chinese medicine classifies this disease as "deficiency in the root and excess in the branch，" with deficiency and stagnation of collateral qi as the root and constraint and stagnation of collateral qi as the branch，where depression arises from deficiency and triggers the disease. Collateral-unblocking therapy based on collateral disease theory fully utilizes the regulatory advantages of multi-target and multi-pathway effects：unblocking intestinal collaterals to free qi and blood circulation，unblocking brain collaterals to regulate the mind and enhance intelligence，regulating qi movement of zang-fu organs and the flow of qi，blood，essence and fluids，restoring the intestine's function of separating clear from turbid substances， and maintaining the brain's clarity. This achieves simultaneous treatment of the intestine and brain in PD patients. This paper discusses the mechanism of collateral- unblocking therapy in treating PD with depression from the perspective of intestine-brain axis regulation，aiming to provide new theoretical paradigms and research methods for the prevention and treatment of neurological diseases like PD with Chinese medicine.