Abstract: Phosphorus doping is a new method for enhancing the reduction of Eu³⁺.This paper investigated the effect of doped phosphorus on the reduction of Eu³⁺ in Sr₃Al₂O₆ and the stability of europium ions.It is shown that the phosphorus can embed into Sr₃Al₂O₆ matrix crystal and change the lattice constant, and yellow-green light-emitting Sr₃Al₂O₆: Eu phosphor can be obtained.The doping of phosphorus can enhance the reduction of Eu³⁺ significantly, but Eu³⁺ in Sr₃Al₂O₆ can not been reduced completely even if the doped phosphorus is enough.The calculation performed from the emission spectra of samples shows that the remained Eu³⁺ in samples has the trend to be reduced when irradiated by high-energy ultraviolet light.