Abstract: Forty male mice(6-week-old) were randomly assigned into four groups according to the body weight. The control group， the high-fat diet group (crude fat contain 18%)， the LA 1 group (highfat diet with 0.05% LA) and the LA 2 group (high-fat diet with 0.1% LA). After 5 weeks feed， the metabolism experiment was carried out. 6 weeks later， the level of the free radical in organizations of the digestive system and the activity of protease， lipase and amylase in the digestive tract were detected. The results showed that feeding the mice with high-fat diet in longterm could improve the level of the free radical in the mice digestive system (P<0.05) and the activity of the lipase in the digestive tract significantly (P<0.05)， decrease the activity of the protease and amylase (P<0.05)， decline the digestibility of the fat， protein (P<0.05) and the sedimentation rate of the protein (P<0.05). Adding 0.05% LA into the high-fat diet could incline the level of the free radical remarkably， enhance the activity of these enzymes and digestibility of the fat，protein and the sedimentation rate of the protein(P<0.05). Adding 0.1% LA into the high-fat diet can recover the level of free radical up to normal level.It was concluded that the high-fat diet could significantly increase the production of the free radical in the mice digestive system，decrease the activity of the digestive enzymes and the absorption of the nutrition. While adding the optimum LA into the high-fat diet could get rid of these disadvantage and relieve the oxidative stress.