Sparstolonin B (SsnB), an isocoumarin compound isolated from the tubers of both Sparganium stoloniferum and Scirpus yagara, has been reported to have anti-inflammatory effects. However, whether SsnB has anti-inflammatory effects on LPS-stimulated 3T3-L1 adipocytes remains unclear. In this study, we investigated the effects of SsnB on adipocyte inflammation in 3T3-L1 adipocytes and anti-obesity properties in high fat diet (HFD)-induced obese rats. 3T3-L1 adipocytes were pretreated with SsnB 1h before LPS treatment. The expression of MCP-1, IL-6, TNF-α, and IL-10 were measured by qRT-PCR and ELISA. The expression of PPAR-γ, TLR4 and NF-κB were detected by western blotting. SsnB was administered to HFD-induced obese rats to confirm its effects in vivo. Our results showed that SsnB dose-dependently inhibited LPS-induced MCP-1, IL-6, and TNF-α production. SsnB was found to inhibit LPS-induced TLR4 expression and NF-κB activition. Furthermore, SsnB was found to activate PPAR-γ and the inhibitory effects of SsnB on MCP-1, IL-6, and TNF-α production can be reversed by PPAR-γ antagonist GW9662. In vivo, SsnB was found to reduce the body weight of rats fed with HFD. SsnB also inhibited the levels of serum triglyceride (TG) and cholesterol (TC) induced by HFD. In conclusion, the results suggested that SsnB could reduce HFD-induced obesity in rats and inhibited LPS-induced cytokines production in 3T3-L1 adipocytes by activating PPAR-γ.