Abstract: An analytical method for the determination of non-derivatized amino acids by HPLC-ELSD was developed. The contents of L-glycine(Gly),L-hydroxyproline(Hyp),L-alanine(Ala)and L-proline(Pro)in Colla Corii Asini and donkey-hide gelatin juice were determined simultaneously. The dried Colla Corii Asini and donkey-hide gelatin juice powder were hydrolyzed with 6 mol·L^-1 hydrochloric acid at 110℃ for 24 h and then analyzed by Thermo hypercarb(150 mm×4.6 mm,5 μm)with methanol-acetonitrile solution containing 0.08% trifluoroacetic acid(90:10)as mobile phase A and water containing 2 mmol·L^-1 perfluorovalerate as mobile phase B with a flow rate of 0.8 mL·min^-1 under the gradient elution. The carrier gas flow rate was 1.5 L·min^-1 and the temperature of drift tube was 55℃. As the results,the four amino acids were completely separated and there was a good linearity in the certain range(r>0.9993). The average recoveries of four amino acids were 97.42%~103.29% and 97.17%~102.19% in the donkey-hide gelatin and donkey-hide gelatin juice respectively with RSD<2.46%(n=6). The developed method was simple,precise and good reproducibility. It could be used to quickly and accurately determine the content of four underivatized amino acids in donkey-hide gelatin and donkey-hide gelatin juice,which was suitable for the quality control of Colla Corii Asini.