Eu2+-doped monophosphates NaSrPO4 and KBaPO4 with the beta-K2SO4 structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay. curves were measured. The phosphors can be efficiently excited by UV-visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu2+ emission, e.g., the. chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO4: Eu2+ and KBaPO4:Eu2+ were obtained from the temperature dependent (10-435 K) luminescence intensities and decay curves. KBaPO4:Eu2+ presents only one emission center; however, Eu2+ ions have a "disordered environment" in NaSrPO4 lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu3+ ions in the F-7(0)-> D-5(0) transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO4, the Eu3+ ions could be distributed in the host with a high "ordered state" in only one site in the lattices. However, the multiple site structure of Eu3+ ions with highly disordered distributions in NaSrPO4 lattices was suggested.