A neutralization hydrolysis route has been used to synthesize titanium oxide nanoparticles. Transmission electron microscopy(TEM) and X-ray diffraction(XRD) characteri- zation results showed the TiO2 nanoparticles were single anatase phases when calcined at 600°C-800°C for 2h. The particle diameter ranged from 15 to 30nm. The pH value was key factor for precursor composition. When pH value 2-4, the H2TiO3 precursor with low agglomeration was obtained. As-prepared anatase TiO2 nanoparticles, during photodegradation of methylic orange under UV-light irradiation(λ=254nm), exhibited excellent activity, more than 95.5% methylic orange was degraded in 1h.