We realized the fabrication of 2D ordered arrays of CdS nanocrystals by nanosphere lithography by use of a monolayer of self-assembled polystyrene spheres 220nm in diameter as a mask. We used scanning electron microscope (SEM) to characterize the structure of samples. The results indicate that the 2D arrays of CdS nanocrystals produced by nanosphere lithography have highly ordered structure which has the same period of the original PS mask. According to the transmission spectrum，it is estimated that the forbidden band width of the CdS nanocrystals is around 2.60eV，which shows a size-dependence of the CdS nanocrystals. This structure has the promising application in the light filter and single-photon emitter.