A series of CdSe-deposited CdS nanowires with different CdSe content were prepared from precursor hexagonal CdS nanowires under different concentration of Na2SeSO3 aqueous solution using hydrothermal method. The phases, compositions, morphologies and optical properties of these composite nanowires were further characterized using XRD, SEM, TEM, UV-Vis, PL and FTIR measurement techniques. The results show that the CdSe with nano-layer crystal deposited on the surface of CdS nanowires exhibits hexagonal wurtzite structure; such CdSe content can be controlled by changing Na2SeSO3 aqueous concentration, reaction temperature and/or reaction time. In comparison with optical properties of CdS nanowires, the absorption range of the nanocomposites becomes much wider, whereas the CdS fluorescence in the nanocomposites shows quenching behavior due to the existence of CdSe, and also, the emission of the CdSe has not been observed. In addition, their optical properties and reaction mechanism are elucidated in detail.