Flower-like and bundle-like hydrated YPO4:Eu3+ hexagonal prism microarchitectures have been synthesized by a CTAB-assisted hydrothermal method. The results from X-ray diffraction and electron microscopy analyses revealed that all as-prepared products were well crystallized hexagonal phase of hydrated YPO4:Eu3+. When the doping concentration of Eu3+ ions changed from 5 mol% to 21 mol%, the morphology of the products could be changed from microflowers to microbundles. Meanwhile, the formation mechanisms of diverse microarchitectures were proposed on the basis of a series of time-dependent experiments. After the samples were annealed at 1000 °C for 3 h, the luminescence properties recovered without a significant morphological change, the reason for the recovery in luminescent intensity is due to the crystal structure changed with the dehydrated samples. Furthermore, the emission intensity of dehydrated phosphors were improved with increase in Eu3+ concentration from 5 mol% to 13 mol% and then decreased for higher concentrations.