Abstract: In order to reduce vitamin loss during the manufacture of compound feeds, a series of experiments taking vitamin C as an example were carried out based on vacuum infusion technology. The experiments included the rate of vitamin C active preservation experiment, the uniformity of coating experiment and the homogeneity between the inner portion and outer portion of pellet experiment. The result indicated that the rate of active preservation increased greatly by liquid coating, the uniformity of coating is mainly decided by the mixing time, the homogeneity is mainly decided by the vacuum degree, the amounts of liquid added, the diameter of pellet. Under the experimental conditions, the optimum parameters of the uniformity of coating were as follows: the mixing time: 6 minutes, the diameter of pellet: Φ2 cm, the spraying pressure: 0.4 MPa; the optimum parameters of the homogeneity between the inner portion and outer portion of pellet were as follows: the diameter of pellet: Φ2 cm, the amounts of liquid added: 4%, the vacuum equalizing time: 160 seconds.