Lyophyllum decastes (Fr.) Singer is an edible fungus prized for its high nutritional value and distinct flavor. China is the world's largest producer of L.decastes. However, research on the influence of geographical conditions on its quality attributes remains limited. This study integrates assessments of nutritional value, bioactive properties, flavor characteristics, and untargeted metabolomics to L.decastes samples from three major producing regions in China: Guizhou (LDG), Fujian (LDF), and Sichuan (LDS). LC-MS/MS-based metabolomics identified 1109 differential metabolites, providing molecular explanations for geographical divergence. Key findings revealed that LDG possessed the most balanced nutritional profile, LDS exhibited the highest bioactivity, and LDF displayed the most intense umami taste. Correlation analysis further confirmed that the overall taste profile is significantly correlated with specific metabolites. Latitude and precipitation showed strong correlations with the quality variation of L.decastes across different regions. These results provide a scientific basis for targeted regional utilization.