The invention discloses monomers and intermediates of an AB type hydroxyl modified high polymer, and preparation methods of the monomers and the intermediates. The intermediates include methyl o-hydroxyl p-carboxyl benzoate (I) and m-hydroxyl p-methoxycarbonyl benzoyl chloride (I'). The monomers of the AB type hydroxyl modified high polymer include a monomer (IV) of AB type hydroxyl modified PPTA (Poly-p-Phenylene Terephthamide) and a monomer (VIII) of AB type hydroxyl modified PBO (Poly-p-phenylenebenzobisthiazole), wherein R1 is H, R2 is OH, or R1 is OH and R2 is OH, and R is CH3 or C2H5. Due to introduction of hydroxyl in the AB type monomer, the light resistance, the composite cohesiveness and the axial pressure resistance of a high polymer prepared from the AB type hydroxyl modified high polymer can be improved, and moreover the preparation methods of the intermediate and the monomer have the characteristics of high yield, high selectivity and industrial production accordance.