To reveal the cellular antioxidant capacity of infant formula milk powder on digestive tract epithelial cells and its mucosal immune cells， five infant formula products were randomly selected from the market and subjected to the cellular models based on rat peritoneal macrophage and human colon adenocarcinoma line Caco-2 cells for determination of their cytotoxic or proliferative effects. A modified Cellular Antioxidant Activity Assay （CAA） method was used to evaluate the cellular antioxidant capacity of the products. Meanwhile， in the absence of exogenous free radical inducer AAPH， the influences of the products on the level of free radicals in cytosol and mitochondria were also investigated， respectively. The results showed that the products of infant formula exhibited neither cytotoxic effects nor proliferative effects against these two cell lines in the concentration range of 40-1 000 μg/mL. Five products showed cellular antioxidant activity in CAA models in both cell lines， but varied obviously in CAA values. In the absence of AAPH， three products showed scavenging effect on the free radicals within cytosol and mitochondrial， the other two， instead， increased the free radical levels within cytosol and mitochondrial.