Monoacylglycerol (MG) and diacylglycerol (DG), as the components of enzymatically synthesized functional oil, were produced by glycerolysis of rice bran oil and glycerol using IM60 (immobilized lipase) in a stirredbatch reactor at 6$0^{circ}C$ for 72 hours. After glycerolysis, the contents of triacylglycerol (TG), DG and MG in the produced functional oil were 41.71%,46.19%, and 11.15%, respectively. The functional oil also contained Phytosterols (2.04$pm$0.17 mg/g), ${gamma}$ -oryzanol (1.06$pm$0.04 mg/g) and $alpha$ -tocopherol (0.13$pm$0.04 mg/g). In animal experiment the dietary effects of functional oil on hepatic acyl-CoA:cholesterol acyltransferase (ACAT) activities of the high cholesterol and high fat (HCHF)-fed mice were investigated. In functional oil-fed group, the liver ACAT activity was significantly lowered than in HCHF and corn oil-fed groups (p < 0.05). This results suggested that the synthesized functional oil may have an atheroproteetive effect by inhibiting ACAT activity.