Rice bean （Vigna umbellata (Thunb.) Ohwi & Ohashi）is an underutilized legume crop with considerable nutritional and health-promoting potential, offering broad prospects for development. In this study, we analyzed four major nutritional components—including protein, starch, total flavonoids, and total polyphenols—in 410 core rice bean accessions. The results showed that protein content ranged from 15.9%-28.2% (mean: 21.0%), starch content ranged from 40.0%-53.7% (mean: 45.8%), while total flavonoid and total polyphenol contents ranged from 1.34-7.39 mg RE/g (mean: 4.10 mg RE/g) and 0.80-2.90 mg GAE/g (mean: 2.19 mg GAE/g), respectively. Based on these results, 34 representative accessions were selected for extensive non-targeted metabolomic analysis, which identified 607 metabolites classified into 12 major categories. The composition of key metabolites classes—such as flavonoids, amino acids and derivatives, alkaloids, and terpenoids—varied among accessions from different geographic origins. Notably, flavonoids were most abundant in accessions from China and Myanmar (19.0% and 19.7%, respectively), while those from Thailand and Laos had higher levels of amino acids and derivatives (20.1% and 18.3%, respectively). This study provides valuable data to support the evaluation, exploration, and breeding utilization of high-quality rice bean germplasm resources.