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The microstructure and superconducting properties of air-processed melt-textured grown Y-Ba-Cu-O samples with the addition of CeO2 precursor of different sizes, e.g. micro-scale and nano-scale were studied. Samples with micro-scale CeO2 addition exhibit an enhanced Jc, which were attributed to the refinement of 211-particles. The mechanism for refining the 211-particles was proposed to be the formation of new nuclei sites from the reaction of CeO2 and Y2-1-1 matrix in the melt-grown process. By reducing the CeO2 precursors to nano-scale from micro-scale, significantly more heterogeneous nucleation site will be introduced with the same amounts of CeO2 additions. And the Jc will be enhanced with the refining of 211 particles. But in this study, it shows the opposite results. The higher Jc value is enhanced by doping micro-scale CeO2. Pinning forces vs. magnetic field studies indicated that both the nano- and micro- CeO2 samples have the same pinning mechanisms as compared with that of the un-doped sample.