The invention relates to a preparation method of yttrium aluminum garnet phosphor activated by cerium and a phosphor. The invention provides a generalized preparation method of yttrium aluminum garnet phosphor activated by cerium. A chemical formula is Y3-x-y-zRyAl5-mGamO12: Cex, R'z. The preparation method comprises the steps of: preparation of metal ions solutions, preparation of precipitant solutions, preparation of metal ions precipitants, addition of flux and solid phase reaction, sintering, grinding powders sintered under high temperature, pickling, alkali washing, water washing and drying, then the target product YAG:Ce phosphor, which has high luminous intensity, low agglomeration degree without ball milling, proper powder size and narrow particle size distribution, is obtained; besides, the phosphor has low agglomeration degree after being treaded under high temperature, and the phosphor can be packed and sealed without ball milling and can maximize the excellent optical property.