The invention discloses a preparation method of an oil well composite paraffin inhibitor, and belongs to the technical field of oil exploitation. The method comprises the following steps: mixing octadecyl methacrylate, maleic anhydride, styrene, an initiator and a solvent, heating and stirring the mixture, and performing a reaction to obtain a mixed solution; mixing and fermenting glass fibers, yeast powder, starch and water, adding pig blood by 0.2-0.3 time by mass of the glass fibers and hirudin by 0.02-0.03 time by mass of the glass fibers, stirring and mixing all the components, and drying, crushing and sieving the mixture to obtain modified glass fibers; and stirring and mixing, by weight, 20-30 parts of the mixed solution, 8-10 parts of the modified glass fibers, 3-5 parts of a surfactant, 20-30 parts of water, 10-20 parts of a modified additive and 10-20 parts of pretreated nano copper powder to obtain the oil well composite paraffin inhibitor. The paraffin inhibitor has an excellent paraffin inhibition effect.