In order to acquire optimum conditions of preparation of yeast extract from its waste residue, single factor experiments were conducted to a good condition of adding external enzymes, and also it was compare with the traditional process. And then the GC—MS was used to analyze the flavor of the yeast extract for determining the best stratagem. Through optimization, the best optimum condition is that it adding 0.20% neutral protease and reacting for 36 h at pH 6.0. The final extract contained a variety of acids, esters, alcohols and other substances. The neutral protease method is shown a better way to acquire yeast extract. Moreover, the products obtained were with rich nutriment.