Abstract: The present paper studies the extraction of mixed amino acids from the waster water of producting cystine process by di-(2-ethyl hexyl)phosphoric acid(P204).The optimum extraction conditions are as follows:P204(0.75)-kerosene(0.15)-2-ethyl hexyl alcohol(0.10),pH=2.5 and room temprature.Deionized water is adopted as stripping agent of mixed amino acids from the loaded organic phase.Extraction and stripping numbers of theoretic stages are 8 and 9 respectively.