The invention discloses a preparation method for a magnolol molecularly imprinted polymer film. The preparation method includes the following concrete steps: both imprinted molecule magnolol and solid-phase reagent are put into a ball mill and ball-milled, so that imprinted molecule inclusion compound is obtained, and the inclusion compound, functional monomer, cross-linking agent and initiator are put into porogen, ultrasonically degasified, then added with bond and ultrasonically stirred, so that mixture is obtained; filter paper is immersed in the mixture, taken out, clamped between two glass sheets, put into an oven and heated to be polymerized, so that polymer is obtained; imprinted molecules are removed from the obtained polymer, and after washing and drying, the magnolol molecularly imprinted polymer film is obtained. The preparation method adopts the mechanochemical technology to include the imprinted molecules, so that the ability of the imprinted molecules in specific binding with the functional monomer is enhanced, as a result, the recognition selectivity of the finally prepared molecularly imprinted polymer film is greatly enhanced, and the magnolol separation effect is good.