A series of nanophosphors of Y1-xPO4:xEu3+（005≤x≤030）were synthesized by a mild hydrothermal method with post heat treatment. The structure and morphology of the samples were characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The results show that these nanophosphors have tetragonal structure with spherical and fine rod-like morphologies in acidic and alkaline condition, respectively, but all are on the nanoscale. The photoluminescence （PL） properties were also investigated under vacuum ultraviolet （VUV） excitation. Compared with samples prepared by solid state reaction, the PO3-4 absorption band located at 142 nm in vacuum ultraviolet region shifts towards high-energy direction. The intensity of 5D0→7F2 （619 nm） emission peak of Eu3+ is higher than that of 5D0→7F1. After heat treatment, the color purity and luminous intensity of the phosphors can be greatly improved. The PL intensity of optimized phosphor is superior to that of samples prepared by solid state reaction. These phenomena can be attributed to the improved crystallinity and reduced defects.