In this study, a series of colloidal ternary semiconductor Zn xCd1-xS nanocrystals are prepared. By controlling the ratios of Zn and Cd, the optical properties of the nanocrystals are modified. When Zn content is 0.5 and 0.8, their PL spectra exhibit two obvious emission peak, in which the narrow and the board bands are attributed to the band-edge and surface state emissions, respectively. Moreover, the quantum efficiency of samples is higher than 30 %, and the particle size distribution is uniform. The optical properties of QDs are affected by the composition instead of their particle size. As a result, it is a new way to fabricate white LED through combining near UV chip with those white QDs and the color temperature can be tuned accordingly.