Parkinson’s disease (PD), the second most common neurodegenerative disorder globally, relies primarily on dopamine replacement therapy for conventional treatment. This approach fails to reverse core pathological processes and is associated with long-term side effects. Recent research on the microbiota-gut-brain axis (MGBA) has revealed that PD pathology may originate in the gut, forming a vicious cycle from the gut to brain through α-synuclein propagation, gut dysbiosis, intestinal barrier disruption, and neuroinflammation. This offers a novel perspective for managing PD through dietary interventions that modulate the gut microbiome. However, single probiotic or prebiotic interventions show limited efficacy. This review systematically introduces the novel concept of “synbiotics combining medicinal plant polysaccharides with probiotics,” aiming to integrate traditional “medicinal food” wisdom with modern microbiome science. The article systematically elucidates the pathological mechanisms of MGBA dysfunction in PD and the intervention mechanisms of probiotics and emphasizes the structural and functional advantages of medicinal plant polysaccharide as superior prebiotics. The core section delves into the multifaceted synergistic mechanisms between these two components: enhancing probiotic colonization and vitality, optimizing microbial metabolic output, synergistically reinforcing the intestinal and blood-brain barriers, and jointly regulating immune and neuroinflammation. This approach targets the MGBA to achieve multi-level intervention for PD.