[en] Multicolored luminescent Cd_xZn_1-xS nanocrystals in aqueous solution have been controllably synthesized with thioglycollic acid (TGA) as a surface modifier. The Cd_xZn_1-xS nanocrystals were characterized by X-ray diffraction (XRD) patterns, transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FT-IR) spectrum, ultraviolet-visible (UV-vis) spectra, and photoluminescence (PL) spectra. From a combination of TEM data and computing methods according to UV-vis spectra and XRD patterns, the particle size of CdS nanocrystal was found to be about 4 nm. Homogeneous Cd_xZn_1-xS nanocrystals have the same well-crystallized cubic lattice structure. FT-IR spectrum indicates that the carboxyl group of TGA is coated on the surface of nanocrystals successfully. The composition dependent UV-vis and PL spectra reveal that the series Cd_xZn_1-xS nanocrystals exhibit good optical properties, which can be modulated by changing the cation molar ratio of Zn:Cd in the reactants. The green and yellow luminescence of Cd_xZn_1-xS nanocrystals is brightly eye-viewable under UV irradiation.