Two experiments were conducted to study the effect of two protein levels and three lysine levels and two methionine levels and three threonine levels on the immune function of piglets. The early-weaned piglets at the ages of 25+or-3 d and 26+or-1 d and body weight of 6.78+or-0.08 kg and 6.68+or-0.04 kg were fed with a simple type diet.