The invention discloses a side-hanging type polymethyl methacrylate rare earth complex luminescent material and a preparation method thereof, belongs to the field of high polymer materials, and in particular relates to a side-hanging type polymethyl methacrylate rare earth complex luminescent material and a preparation method thereof. The side-hanging type polymethyl methacrylate rare earth complex luminescent material is obtained by taking polymethyl methacrylate random copolymer of side-hanging aromatic carboxylic acid as a high polymer ligand and organic small molecules as a co-ligand to perform coordination with rare earth ions in an organic solvent. According to the side-hanging type polymethyl methacrylate rare earth complex luminescent material disclosed by the invention, because the luminescent center of the material is side-hung on a high polymer main chain, and flexible high polymers wrap the luminescent center and are separated from the luminescent center, a concentration quenching effect is effectively eliminated, and the fluorescence intensity of the luminescent material can be enhanced along with the increase of the rare earth content; and moreover, a matrix polymer has good transparency, has good solubility in various organic solvents, can be prepared into solid powder, a transparent film or nano fibers, can emit fluorescent light of various colors under ultraviolet irradiation, and can be applied to the fields of anti-counterfeiting mark materials, display materials and the like.