A low temperature co-fired ceramic powder has a chemical composition of xR2O-yR′O-zM2O3-wM′O2, wherein R is Li, Na and/or K, R′ is Mg, Ca, Sr, Ba, Zn and/or Cu, M is B, Al, Ga, In, Bi, Nd, Sm, and/or La, M′ is Si, Ge, Sn, Ti, and/or Zr, x≧0, y≧0, z≧20%, w≧15%, and x+y+z+w=1. The preparation method comprises: weighing constituent powders according to the composition of the ceramic powder, and uniformly mixing these powders as a raw material powder; and presintering the raw material powder in a muffle furnace followed by grinding, the presintering comprising gradiently heating the raw material powder to a maximum temperature of 950° C. by first rising to 350-450° C. and staying thereat for a period, then staying at intervals of 50-100° C. for a period.