Abstract: The near-field excitation fluorescence characteristic of quantum dots (QDs) streptavidin conjugate is studied by use of scanning near-field optical microscopy (SNOM). Owing to the high imaging resolution of SNOM, as well as the high intensity and narrow emission spectra of QDs, the high contrast near-field fluorescence images were obtained, and the full width at half maximum(FWHM) of the single QDs is approximately 25nm, meanwhile the single and assemble quantum dots were observed. For another, the photostablity and fluorescence intensity of QDs and that of a conventional organic fluorescence dye FITC were compared, it is founded fluorescence intensity of QDs were higher and than that of FITC. If the excitation intensity is 300W/cm2, there isn't obvious fluorescence intensity change in QDs for more than 6 hours illumination, but fluorescence intensity of FITC rapidly faded for less than 1 hours illumination, it indicates that