The effects of N-doping on the bead-milling dispersion behaviors and optical properties of ruble TiO2 nanoparticles have been investigated and compared to those of bare TiO2. N-doped rutile nanoparticles were prepared by mixing TiO2 powder with urea, and heating the mixture at 800 degrees C for 3 h. The nitrogen elements in the N-doped TiO2 samples were confirmed by electron dispersive X-ray spectroscopy (EDS) and Raman analysis. The N-doped TiO2 nanoparticles were then dispersed by bead milling with small beads in diglyme using APS as a dispersing agent. The resulting N-doped rutile powders were transparent and colorless suspensions, whereas the dispersed bare rutile powders were yellow. The formation of colorless suspensions by the N-doping process was investigated using a model of the interaction of the N-doped TiO2 surface with the adsorbed dispersant in conjunction with the Rayleigh scattering mechanism.