Butter serum (BS) is a byproduct of anhydrous butter production and a natural milk byproduct. There are two main sources: one was the water phase obtained by melting and centrifugation, and the other was using 75% dilute cream to convert the phase to obtain butter serums. There were few studies on the components and their functional characteristics of butter serums at home and abroad, which limited the reuse value of butter serums. The component composition and application characteristics of butter serums were analyzed in this experiment. By centrifugation and other methods the cow butter serums was successfully isolated, and the basic and fat bulb membrane source components of butter serums were analyzed by using raw milk and buttermilk as controls. The results showed that the protein and fat contents of butter serums were increased significantly, and the total calcium content was decreased significantly, without lactose, moisture and pH value (P>0.05). Using liquid phase mass spectrometer, butter serums contained 56 kinds of fat globular membrane phospholipids, of which sphingomyelin content reached 0.352mg/mL;the fat globular membrane protein of butter serums accounted for 23.32% of the total protein. The effects of butter serum and buttermilk on emulsion emulsification were compared. The results showed that the emulsification of butter serum was significantly better than that of buttermilk (P<0.05). The emulsifying activity and stability of butter serum reached the maximum at 3% concentration, which were 2.682m2/g and 91.1%, respectively. In conclusion, butter serum contained abundant fat globule membrane source components, and the emulsification property of butter serum was better than that of buttermilk at the same concentration, which had higher application potential.