As the major biologically active constituents in Ganoderma species, Ganoderma triterpenoids (GTs) also showed potential anti-obesity effect in recent reports. To further elucidate the anti-obesity effect of GTs, four new compounds Ganoderenses H-K (1-4) and four known compounds (5-8) from Ganoderma resinaceum were determined by extensive spectroscopic analysis. The absolute configurations of Ganoderenses H (1), I (2), and Resinacein S (Res S; 5) were confirmed for the first time by X-ray crystallographic analysis. Then the effects of these triterpenoids on brown/beige adipocytes were further analyzed in vitro. Our results may be summarized as follows: (1) Res S reduced lipid droplets size by regulating lipid metabolism, but not affect the differentiation of C3H10T1/2 cells. (2) Res S increased the expression of brown and beige adipocytes markers and enhanced the activity of brown and beige adipocytes (e.g., increased beta-oxidation and pro-lipolytic activities et al.) in differentiated C3H10T1/2 cells. (3) Res S induced mitochondrial biogenesis and increased mitochondrial OCR in differentiated C3H10T1/2 cells. In conclusion, Res S is potential for activating the function of brown and beige adipocytes, thus having potential therapeutic implications for obesity and associated metabolic diseases.