The disclosure relates to display technology field, especially relates to a polymer dye and a method for preparing the same, a photoresist composition, a color photoresist, and a display device. The polymer dye is formed by the copolymerization of an acrylated dye represented by General Formula I and an acrylic acid or acrylate represented by General Formula II, in General Formula I, Dye represents a residue of a dye containing an aromatic hydroxyl group or an aromatic amino group, R1, R2, and R3 are each independently selected from a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms; in General Formula II, R4, R5, R6, and R7 are each independently selected from a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms; the mole numbers of the acrylated dye represented by General Formula I and the acrylic acid or acrylate represented by General Formula II are x and y, respectively, and x:y=1:0.05-10; and the weight average molecular weight of the polymer dye is 2000-50000. The color photoresist produced employing the technical solution of the present disclosure avoids flooding, and improves the display quality of the display.