The present invention provides a phosphor of formula A2SiO5:B (A is Y or Gd, and B is Ce or Tb) which is characterized by a surface elemental composition represented by (A+B)/Si ranging from 1.5 to 2.5, wherein A is Y or Gd, and B is Ce or Tb; and method for preparing said phosphor. One embodiment of the method is as follows: a SiO2 powder is mixed with co-precipitate (Y, Ce)2O3 (Ce/Y=0.01), in an amount ranging from 10 to 110 mol % based on the amount of (Y, Ce)2O3, and the mixture is charged into the inner crucible of a double-walled aluminum crucible. After graphite is charged between the inner and outer crucible, the mixture is calcined at 1450° C. for 2 hours to obtain an Y2SiO5:Ce phosphor. The luminous efficiency of a field emission display (FED) prepared employing the Y2SiO5:Ce phosphor was measured at an anode voltage of 600V, an electric power input of 30 Wp-p and a duty rate of 1/240. It is desirable that the relative amount of SiO2 based on the amount of (Y, Ce)2O3 ranges from 40 to 70 mol %, preferably 50 to 60 mol %.