The amino acid contents of extractable proteins from natural rubber latex (NRL) deporteinized with the basic proteinase were determined by OPA-FMOC precolumn derivatization reversed high performance liquid chromatography (HPLC) after chonie acid hydrolysis. The deproteinized effect was evaluated by the variation in the total amino acids and the effects of the selected proteinase on the proteolysis of extractable proteins were investigated by the variation in the contents of 16 sorts of amino acids. The results indicate that athe peptide bonds of the extractable proteins in NRL can be proteolyzed by the selected proteinase and compositions of amino acids from proteins are vaiable during the proteolysis. The determined minimum of extractable proteins from NRL is 1.5 ugh/ml (sampling 5 mew g, S/N=2) and the results are not affected by the compositions of amino acids from proteins. By comparing with the composition of amino acids of BSA, this method is precise and accurate.