Abstract: Two nitrogen-balance experiments were conducted to determine the optimum balance pattern among the four amino acids (lysine,methionine,tryptophan and threonine) in the diet on digestible basis for piglets (10kg) challenged with lipopolysaccharide or with saline as control.The method of amino acid deletion was adopted.All pigs were of a single genetic background and geographical site of origin.In each group fifteen Landrance×Rongchang castrated piglets were allotted randomly to one of five groups of dietary amino acid regimens. Positive control group was supplemented with four amino acids. One of the four amino acids was deleted by about 25% in the respective treatment groups. After the nitrogen-balance experiments,the slaughter technique was introduced to determine the ideal amino acid digestibility of the positive control by using chromium oxide(3g/kg) as the indicator. The results showed that the ideal amino acid pattern of Lys∶Met∶Thr∶Trp on the digestible basis was 100∶27∶29∶59 for 10-kg pigs under immunologic stress, and 100∶30∶21∶61 for piglets under normal condition.