Based on the determination of free amino acids (FAAs) in 12 varieties amino acid preparations sold in the market, the amino acid preparations could classified into three classes: the nutrimental, the remedial and the carrier preparation. According to the ratios and the recommended by FAO, the nutritive values of the proteins in the nutritional preparation were evaluated. It was found that the amino acids in some oral preparation contained less methionine and/or isoleusine with an unreasonable ratio of amin...