This experiment was conducted to study the effects of amino acid on growth limitation of ruminal protein-degrading bacteria (R.amylophilus, B.fibrisolvens and P.ruminicola) in vitro. Four Xuhuai goats fitted with permanent ruminal cannula were used to provide rumen liquor in vitro and the rumen liquor was cultivated by the artificial simulation rumen fermentation device. The specific amino acid default method was applied, and 5 groups of total amino acid group, methionine default group, lysine default group, branch-chain amino acid default group, aromatic amino acid default group were designed. The results showed as follows: there was a certain limitary role of specific amino acid default on the growth of R.amylophilus, B.fibrisolvens and P.ruminicola. The order of the limitary role of specific amino acid on the R.amylophilus, B.fibrisolvens and P.ruminicola growth (compared with the total amino acid group) was aromatic amino acid>lysine>branch-chain amino acid>methionine; lysine>aromatic amino acid>branch-chain amino acid>methionine; branch-chain amino acid>aromatic amino acid>methionine>lysine, respectively. In conclusion, amino acid default could influence the growth of the ruminal protein-degrading bacteria in vitro.［Chinese Journal of Animal Nutrition, 2010，22（1）:88-92］