Abstract: The vitro digestion of sialic acid for infant formula milk powders was conducted in a simulating digestion environment of infant, and human milk was used for comparison. The gastric, intestinal and total in vitro digestibilities of sialic acid were measured.The result showed that sialic acid in human milk and infant formula were mainly digested in the intestines; it was also found that when dry production addition amounts was 2.8kg /t, the sialic acid in infant formula were closed to human milk in vitro digestibilities.