Part of the amino acids contained in fossil bones from deposits in the localities of "Peking man", "Lantian man" and "Yuanmo man" has been analysed by gas chromatographic method. They are alanine, valine, glycine, isoleucine and alloiso-leucine, leucine (+β-alanine), proline (+ threonine), serine, r-ABA, methionine, hydroxyproline, phenylalanine, aspartic acid, glutamic acid and lysine. The main constituents of the fossil bones are gly., glu., ala., pro., asp., and so on. With increase in geological age of the sample, the total amount of amino acids and content of unstable amino acids decrease, but the alleu/iso. ratios increase with geological age.In this article the authors also tried to estimate the geological age of "Peking man" with application of the racemization of isoleucine.