Abstract: Polysaccharides are the main bioactive constituents of Polygonatum cyrtonema. To screen lactic acid bacteria strains for their ability to enhance polysaccharide accumulation during Polygonatum cyrtonema Hua fermentation, optimize the fermentation process parameters, and evaluate the prebiotic potential of the fermented product. Twelve laboratory-preserved Lactiplantibacillus plantarum strains, originally isolated from traditional fermented foods, were used as starter cultures for P. cyrtonema fermentation. Initial single-factor experiments systematically evaluated the effects of three critical parameters: fermentation duration (0~144 h), inoculum size (0~9% v/v), shaking rate (0~200 r/min) and temperature (20~40 ℃) on polysaccharide yield. To optimize the fermentation process of P. cyrtonema by response surface methodology (RSM) and assess the prebiotic activity of the lyophilized powder. The results showed that all L. plantarum strains could grow normally in nutrient-free P. cyrtonema medium, achieving peak biomass (1×10⁸ CFU/mL) within 24~48 h, followed by rapid decline. Strain L6 showed superior performance, increasing polysaccharide content by 25% after 48 h fermentation. RSM-derived optimal conditions (3.8 days, 2.5% inoculum, 35 ℃) produced a polysaccharide yield of 1.30 mg/mL, achieving a 57.71% increase over the baseline. Analysis of the fermented polysaccharides revealed a notable increase in molecular weight, along with structural modifications in the pyranose rings. Specifically, the degradation of monosaccharides such as mannose and glucose was observed, while the levels of galactose and galacturonic acid increased significantly. Moreover, the fermented product significantly enhanced the growth of three probiotic strains: L. plantarum CICC22213, L. rhamnosus CICC22175 and L. casei FBKL1.3022. The production of primary short-chain fatty acids, lactic acid and acetic acid, was found to be biomass-dependent. These results demonstrated that strain selection coupled with process optimization can significantly improve polysaccharide accumulation in P. cyrtonema. The fermented product exhibits promising prebiotic properties, supporting its potential application in functional food development using this medicinal rhizome species.