A series of Sr₃Y(PO₄)₃:Eu₂₊samples are synthesized by the high temperature solid-state method. Sr₃Y(PO₄)₃:Eu₂₊shows an asymmetrical emission band under excitation of 350 nm. The emission peaks at 426 nm and 497 nm are assigned to the nine-coordination Eu₂₊and six-coordination Eu₂₊, respectively. The effects of Eu₂₊ doping content on the emission intensity and color are observed, and the concentration quenching effect is also observed. For two different Eu₂₊luminescence centers, the quenching mechanisms are dipole-dipole interaction and quadrupole-quadrupole interaction, respectively. And the critical distance of energy transfer is calculated by concentration quenching and turns out to be about 3.67 nm. The results above show that the asymmetrical emission band of Sr₃Y(PO₄)₃:Eu₂₊ comes from two different Eu2+₂₊ luminescence centers in the lattice.