The effect of L-and D-Phenylalanine (Phen) on the growth kinetics and morphology change of alpha L-Glutamic acid(L-Glu) was investigated using the method of single crystal in the flow system. With L-Phen the growth rate of L-Glu crystals in the direction parallel to the main plane decreased and the growth became to be irregular. However, no influence was observed in the direction of thickness. New face determined as (110), indicating that L-Phen adsorbs on that face. From crystallographic data the effect of L-Phen could be explained. However, more complicated mechanism for the morphology change was suggested. No effect of D-Phen means that the additive effect is highly stereo-selective.