Several studies had indicated that the whole body of sea cucumber had beneficial effects on lipid metabolism. However, little information has been known on the individual functions of its bioactive components, and this study was undertaken to compare the different effects on improving lipid metabolism. The rats were assigned to seven groups: control, whole sea cucumber, saponins, polysaccharides, collagen peptides, dregs and non-saponin residues. After 28 d of feeding, the serum total cholesterol, triglyceride, high-density lipoprotein-cholesterol, and hepatic lipid concentrations were examined. The results indicated that a dietary saponin supplement significantly suppressed adipose accumulation, and reduced serum and hepatic lipids. Saponin proved to be more effective than the other isolated components, so is considered to be the main lipid-lowering component in sea cucumber. The possible mechanism by which saponins improved lipid metabolism was also investigated. The saponins of sea cucumber suppressed and delayed TG and TC absorption which could be related to the pancreatic lipase inhibiting effect of saponins. This may be an important mechanism to explain its lipid-lowering effect on rats.