A simple chemical conversion method has been demonstrated to synthesize mesoporous LuPO4: Ln3+ (Ln = Eu, Tb, Dy, Sm) phosphors with high crystallinity and uniform morphology using the Lu4O(OH)9NO3 as a sacrificial precursor and H3PO4 as a phosphorus source. We proposed that the employment of a thermally stable, highly crystalline, and large surface area mesoporous LuPO4 as the doped matrix was the key for fabricating phosphors, which not only enhanced light harvesting into the surface of LuPO4 and interaction with their structures but also maintained the structural stability. Transmission electron microscopy (TEM), X-ray diffraction, and nitrogen sorption results demonstrated that the obtained mesoporous materials were consisted of numerous crystalline nanoparticles and possessed closed-packing mesostructures. The synergetic effect of high crystallinity and large surface area in these materials resulted in excellent photoluminescence performance. Upon ultraviolet excitation, the corresponding Ln3+ ions doped LuPO4 phosphors showed their characteristic f-f emissions and gave orange red, green, blue-white, and white emission, respectively. These merits manifested that the mesoporous LuPO4 phosphors may have potential application in the field of color display.