Abstract: The aim of this experiment was to study the effect of chito-oligosaccharide on serum immune function of piglets and to determine the optimal dosage of chito-oligosaccharide in piglets. A total of 200 healthy, 28-day-old weaned three-way hybrid piglets were divided into 4 treatment groups with 5 replicates according to the single-factor experiment design. At the later stage of the experiment, the immune indexes in the serum of piglets were detected, and it was concluded that adding proper amount of chito-oligosaccharides in the feed of piglets can effectively enhance the cellular and humoral immune functions of piglets.