Glutamate, asparate, glycine, taurine and GABA in brain were seperated and determined by HPLC system of the automatic processes of precolumn o phthaldialdehyde derivatization and injection. Average coefficient of variation for peak areas of 5 amino acids was 2.0±1.3% with the detection limit of 50ng. Average line coorelation coefficient was 0.97±0.03.