CdS0.13Se0.87 nanocrystals of different sizes were grown by annealing glass contained Cd,Se and S at 650—800℃ for 4?h. The absorption spectra, photoluminescence spectra and electroabsorption spectra of the nanocrystals were measured. The energy of part of the electronic states was determined. Dependence of the optical properties of nanocrystals on their size was discussed. With the increase of nanocrystal size, the absorption, photoluminescence and eletroabsorption shifted red due to the weakening of quantum size Stark effects. The electroabsorption of small nanocrystals was due to the quantumconfined Stark effects whereas the electroabsorption line shape of larger nanocrystals was similar to that of bulk materials. With the increase of nanocrystal size, the electroabsor ption is enhanced. All nanocrystals have the third\|order optical susceptibility.