A preparation method of a precursor of a rare earth activated alkaline earth metal fluorohalide stimulable phosphor is disclosed, comprising (A) adding an aqueous solution of an inorganic fluoride into a mother liquor containing a barium halide to form a reaction mixture containing a precipitate of a precursor of the stimulable phosphor, and (B) removing a solvent from the reaction mixture to obtain a concentrated reaction mixture, wherein the steps (A) and (B) are concurrently performed over periods of a and b, respectively, and meeting the following requirement: 0.25