A marine formula composed of Ulva lactuca extraction and enzymatic hydrolysates was extracted from Dosidicus gigas skins. In vitro assay demonstrated that the marine formula possessed good antioxidative activities, EC50 (effective concentration of antioxidant substance removing 50% of free radicals) on DPPH free radical scavenging activity, chelating activity of Fe2+, reducing power and SOD-like activity were 0.54, 4.52, 1.61 and 5.98 mg/ml, respectively. The aim of this study was to evaluate the effect of the marine formula against lipid accumulation by using 3T3-L1 peradipocytes. At 2.5, 5 and 10 mg/ml, the marine formula demonstrated no cytotoxicity to peradipocytes; however, it could inhibit differentiation of mature adipocytes. In terms of lipid accumulation, the results showed that 2.5, 5 and 10 mg/ml of the marine formula could inhibit lipid accumulation, decreasing the triglyceride contents and glycerol-3-phosphate dehydrogenase activity in a dose-dependent manner.