Abstract: A new type of CdTe quantum dots(QDs) was prepared. The method was established to determine the mixed amino acids in Luohanshen by CdTe as fluorescent probe. After adding the Co2 +fluorescent quantum dots into the CdTe solution,the fluorescence intensity reduced. The reduced extent had a linear relationship with the concentration of Co2 +in a certain range. After adding the amino acids,the fluorescence intensity restored,and the quantum fluorescence intensity was linear with the concentration of amino acids. In the mixed acids standard solution with the linear range of 2.0×10-8mol/L to 5.5×10-7mol/L,the linear equation of the recovery intensity of quantum dots fluorescence and the mixed acids concentration was y =1.04 ×106x +1.013. The correlation coefficient was R2=0.9995. The influence factors on the system caused by the different buffer solution,p H value and Co2+concentration,etc were examined. The result showed that,in borax buffer solution with p H=9.5,the Co2+solution 2.0×10-5mol/L could be better CdTe fluorescence. The relative standard deviation used to measure the acture sample(n=5) was 3.0%. The recovery rate was between 98.3% to 104.4%.The detection limit was 1.1×10-8mol/L. The method was simple,rapid and practical.