Abstract: Host doped (Y,Rn)₂O₂S:Sm³⁺,Ti⁴⁺,Mg²⁺ (Rn=La, Gd, Lu, Ga, Al) red phosphors were prepared by solid state method. Their chief emission peaks are in the red-orange range coming from the energy transition of ⁴G_5/2→⁶H_7/2 and host-doping has little effluence on the emitting spectra. Afterglow results show that the semi diameter of doped ions has some effect on the longlasting property. When the doped ion is a little smaller than Y³⁺, the afterglow time will increase. When two ions are doped, two smaller ions doping will promote the long-lasting property; if one ion is larger than Y³⁺, it will shorten the long-lasting time. The presumable mechanism was also discussed.