Abstract: To increase the contents of saponins and polysaccharides in Panax quinquefolius L., and enhance its functional activity and application value, this study took Panax quinquefolius L. as the raw material to screen characteristic lactic acid bacteria strains capable of improving the contents of total saponins and polysaccharides. The screened strains were identified through morphological observation, physiological and biochemical tests, and 16S rDNA molecular biological analysis. The biotransformation process of the characteristic strains was optimized via single-factor experiments and orthogonal tests. High-performance liquid chromatography-mass spectrometry (HPLC-MS) and spectrophotometry were adopted to analyze the changes of chemical compositions in Panax quinquefolius L. before and after biotransformation. Chemical methods were used to determine the in vitro antioxidant, hypoglycemic and hypolipidemic capacities of total saponins and polysaccharides before and after transformation.The optimal strain was identified as Pediococcus pentosaceus. The optimal biotransformation conditions were determined as follows: solid-liquid ratio of 1:10 (W/V), inoculum size of 6% (V/V), incubation time of 6 days, and incubation temperature of 37 ℃. Under these conditions, the contents of total saponins and polysaccharides in the transformed product increased by 53.07% and 119.50%, respectively. HPLC analysis showed that the contents of ginsenosides Rg1, Rb2 and Rb3 increased, while those of Re, Rf, Rb1, Rc and Rd decreased after transformation. The relative contents of macromolecular ginsenosides such as Rc and Rb1 were reduced, whereas the relative contents of small-molecular ginsenosides including Rg3 and F2 were elevated after biotransformation. Moreover, the in vitro antioxidant, hypoglycemic and hypolipidemic abilities, as well as the improvement effect on oxidative stress in PC12 cells of total saponins and polysaccharides were significantly enhanced after transformation (P<0.05).The results indicated that the screened Pediococcus pentosaceus could significantly increase the contents of total saponins (including rare ginsenosides) and polysaccharides in Panax quinquefolius L. This study provides a theoretical basis and technical support for the resource utilization of Panax quinquefolius L. and the development of its functional foods.