Water-soluble CdTe quantum dots (QDs) stabilized by thioglycolic acid (TGA) with high quantum yield were synthesized. And the small biomolecule 17beta-amino-estradiol was marked successfully by CdTe QDs. The analysis of UV-Vis spectroscopy, fluorescence spectroscopy, infrared spectroscopy and inverted microscope photographs showed that the surface carboxyl of CdTe quantum dots conjugated with the amino of 17beta-amino-estradiol through the activation of N-hydroxysuccinimide. 17beta-amino-estradiol marked by CdTe QDs successfully provided an experimental basis for new drug screening model.