This study evaluated the biotransformation of active compounds and antioxidant activity in liquorice root following solid-state fermentation with the food- and medicine-homologous white-rot fungus Pleurotus ostreatus HXS-M1. Dried slices of Glycyrrhiza uralensis were moistened to 65 % moisture, autoclaved, cooled, and inoculated with 4 % (v/w) seed mash that had been pre-cultivated in potato-dextrose broth for seven days at 28 °C. Fermentation proceeded under static conditions at 28 °C for 25 days, after which the substrate was dried at 40 °C, ground to 40 mesh, and extracted with 70 % ethanol. HPLC-DAD analysis showed that the process completely removed liquiritin (100 % decrease, P < 0.01) and lowered glycyrrhizic acid by 59.41 % (P < 0.01), whereas the pharmacologically active aglycones liquiritigenin and glycyrrhetinic acid increased by 270.29 % and 390.23 %, respectively (P < 0.01). Concomitantly, ABTS⁺ radical scavenging improved from 64.19 % to 129.78 % and DPPH· scavenging from 72.48 % to 228.53 %, corresponding to 102.18 % and 215.30 % enhancements (P < 0.01). These results demonstrate that P. ostreatus HXS-M1 efficiently hydrolyses oleanane-type saponins and flavonoid glycosides into their more lipophilic and antioxidant aglycones, offering a green, low-cost bioprocess for upgrading liquorice for nutraceutical, pharmaceutical and feed applications.