Abstract: Aqueous silicon carbide quantum dots(QDs) without cytotoxicity were prepared via a simple chemical etching method with the mixture etchants of nitric and hydrofluoric acid and then ultrasonic dispersion and centrifugation. The microstructure and optical properties were measured and fluorescent imaging for living cells of Aureobasidium pulluans was investigated. The microstructure inspection results indicated that silicon carbide QDs were nearly spherical feature, 2.5 nm of diameter which was shorter than its' Bohr diameter(5.4 nm). The remarkable photo luminescence(PL) effect was displayed when it was excited. In the scope of 320 nm to 360 nm for exciting light wavelength, the emission light intensity reached the top. The red shift for PL occured with the increasing of exciting light wavelength. The blue shift of emission light for PL occured with the diameter decreasing of SiC QDs. Further research results indicated that there was no cytotoxicity of SiC QDs and hardly affected the growth, physiological function of the living cells with the potential application of long-time- cultivating image. Moreover, mechanism and specificity of mark of QDs were also analyzed.