Objective To investigate the effect of oil with medium-long-chain triacylglycerols on blood lip- id and lipoproteins in hyperlipemic patients. Methods Totally, 112 patients with hypertriglyceridemia were en- rolled and randomly divided into MLCT group (consumed oil with medium-long-chain fatty acids) and LCT group (consumed oil with long-chain fatty acids) (both 25-30 g/d for 8 weeks). Patients in both two groups were also instructed to take exercises. Height and weight were measured at baseline and 8 weeks later. Blood glucose, serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total cholesterols (TC), triglyc- erides (TG), high density lipoprotein cholesterol, low density lipoprotein cholesterol, apolipoprotein Al (ApoAl), ApoB, ApoA II , ApoC2, ApoC3, and ApoE were measured and compared. Results At the end of study, 101 subjects were included. There were 50 subjects left in LCT group and 51 subjects left in MLCT group, respectively. There was no significant difference in weight, ALT, AST, TC, and TG at baseline between two groups (P>0.05). Eight weeks later, weight, serum TG, ApoC2, and ApoC3 were significantly lower and ApoAl level was significantly higher than those at baseline in MLCT group (P < 0.05). At the end of study, the decreases in body weight and blood biochemical variables including TG, ApoB, ApoA II , ApoC2, ApoC3 were significantly much greater in MLCT groups than those in LCT group (P < 0. 05). Conclusion When the diet is reasonably controlled, oil of medium-long-chain triacylglycerols may reduce the concentration of TG and improve the levels of apolipoproteins.