To evaluate the antioxidative activity of yak milk casein hydrolysates in vitro, HepG2 cells were treated with H₂O₂ to establish the oxidative model. The protein carbonyl content and the activity of SOD, GSH-Px and CAT of HepG2 cells pretreated with yak milk casein hydrolysates were measuredto analyze the antioxidative activity of yak milk casein hydrolysates. The results showed that pretreatment with yak milk casein hydrolysates significantly alleviated the increase of protein carbonyl content induced by H₂O₂ and increased the activity of SOD, CAT and GSH-Px, suggesting the antioxidative capacity of yak milk casein hydrolysatesin vitro. The results suggested that yak milk casein hydrolysates possess protective effects against H₂O₂-induced oxidative damage in HepG2 cells, whichprovide a basis for the further utilization of yak milk resources and forthe application of the bioactive peptides as antioxidant functional foods.