ZnO nano-fibrous thin films with various precursor concentrations ranging from 0.2 to 1.0 mol (M) were grown by spin-coating method and effects of the precursor concentration on surface and optical properties of the ZnO nano-ribrous thin films were investigated by using scanning electron microscopy (SEM) and photoluminescence (PL). ZnO nuclei were formed at the precursor concentration below 0.4 M and the ZnO nano-fibrous thin films were grown at the precursor concentration above 0.6 M. Further increase in the precursor concentration, the thickness of the ZnO nano-fibrous thin films is gradually increased. The intensity and the full-width at half-maximum (FWHM) of the near-band-edge emission (NBE) is increased as the precursor concentration is increased. The deep-level emission (DLE) is red-shifted as the precursor concentration is increased.