YBO3:Eu3+ microspheres were synthesized by a hydrothermal method. Size and surface morphology of the spheres were tailored by ion-adding. Phase identification, morphology observation, and photoluminescence (PL) performance of the YBO3:Eu3+ microspheres were characterized byX-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and PL spectrophotometer, respectively. Moderate particles with enlarged size and perfect surface were achieved by adding Li+ ion or/and Mg2+ ion. PL emissions of such YBO3:Eu3+ phosphors were enhanced. Significantly improved PL intensity was achieved when 1% Li+ ion and 5% Mg2+ ion were added, which was nearly doubled compared with the reference sample.