A phosphor can be excited by UV, purple or blue light LED, its preparation method, and light emitting devices incorporating the same. The phosphor contains rare earth, silicon, alkaline-earth metal, halogen, and oxygen, as well as aluminum or gallium. Its General formula of is aLn2O3.MO.bM′2O3.fSiO2.cAXe:dR, wherein Ln is at least one metal element selected from a group consisting of Sc, Y, La, Pr, Nd, Gd, Ho, Yb and Sm; M is at least one metal element selected from a group consisting of Ca, Sr and Ba; M′ is at least one metal element selected from Al and Ga; A is at least one metal element selected from a group consisting of Li, Na, K, Mg, Ca, Sr and Ba; X is at least one element selected from F and Cl; R is at least one metal element selected from a group consisting of Ce, Eu, Tb and Mn; 0.01≦a≦2, 0.35≦b≦4, 0.01≦c≦1, 0.01≦d≦0.3, 0.01≦f≦3, 0.6≦e≦2.4. The phosphor has broad emitting range, high efficiency, better uniformity and stability. A light emitting device is obtained by incorporating the phosphor into a UV, purple or blue light emitting device.