In this paper, we prepared carbon doped nanocrystalline ZnO by pyrolyzed zinc stearate at 250°C and 300°C respectively. The XRD curves indicate the sample has polycrystalline hexagonal wurtzite structure. The XRD data of the sample prepared at 250°C and 300°C has a bigger angle shift about 0.05°and 0.3°respectively. That indicate the structure of the sample has some changes. The EDS indicate the sample contains Zn, O and C. So the XRD shift may attribute to the C. The XPS indicate the C doped in the crystal lattice of ZnO of the sample prepared at 300°C, and the sample prepared at 250°C may be only a few of C doped in the crystal lattice of ZnO. The PL of the sample prepared at 300°C only has a weak ultraviolet emission, which indicates C modified the nanocrystalline ZnO surface as a non-radiative recombination center. In this process C could non-radiatively recombine the carries on the nanocrystallin ZnO surface. The sample prepared at 250°C has a strong visible emission at about 530 nm. This emission band could be attributed to oxygen vacancy because C schlepped some oxygen on the nanocrystalline ZnO surface.