In order to explore the effects of milk fat aggregation caused by thermal processing on the digestion and absorption characteristics of milk fat and lipid metabolism， the changes of fat particle size， potential and lipolysis rate during the digestion of aggregated milk fat and non aggregated milk fat were measured by vitro simulated digestion； The contents of fat in feces， triglycerides and cholesterol in serum and liver at different times were measured by animal experiments. The average particle size of aggregated milk fat group in the stomach (7.40 μm) was significantly increased (P<0.05) compared to the initial stage(4.54 μm). The average particle size of non aggregated milk fat group in the stomach (9.26 μm) was also significantly increased (P<0.05) than the initial stage (2.80 μm)； The amplitude of potential change in the aggregated milk fat group was smaller than that in the non aggregated milk fat group. The release rate and degree of fatty acids in the aggregated milk fat group are lower than those in the non aggregated milk fat group， indicating that the digestion speed of aggregated milk fat is slower than that of non aggregated milk fat. The results of in vivo experiments in rats showed that the fat excretion rate of the aggregated milk fat group (8.68%) was higher than that of the non aggregated milk fat group (6.66%)， indicating a low bioavailability of aggregated milk fat. After 6 hours of gavage， the serum triglycerides (0.57 mmol/L) in the aggregated milk fat group were significantly higher (P<0.05) than those in the non aggregated milk fat group (0.45 mmol/L)， and the cholesterol (1.76 mmol/L) in the aggregated milk fat group was also significantly higher (P<0.05) than those in the non aggregated milk fat group (1.46 mmol/L)； The liver triglycerides (0.0090 mmol/L) in the aggregated milk fat group were significantly lower (P<0.05) than those in the non aggregated milk fat group (0.0117 mmol/L)， and the cholesterol (0.0058 mmol/L) in the aggregated milk fat group was also significantly lower (P<0.05) than those in the non aggregated milk fat group (0.0069 mmol/L)， indicating that the aggregation of milk fat also affects lipid metabolism. Therefore， through the vitro model digestion system and rats gavage experiment， we found that the aggregation of milk fat will affect its digestion and absorption and lipid metabolism in rats.