The invention relates to the field of drilling fluids, and discloses an oil-base drilling fluid tackifier and a preparation method thereof. The preparation method comprises the following steps: (1) in the presence of an initiator, carrying out polymerization reaction on a water-phase solution containing unsaturated amide, unsaturated organic sulfonate and unsaturated organic carboxylic acid with an oil-phase solution containing an emulsifier and base oil to obtain a polymer emulsion; (2) purifying and drying the polymer emulsion to obtain a composite; and (3) mixing the composite, meerschaum powder and acid by stirring, and drying the mixture. The oil-base drilling fluid tackifier can overcome the defect of lack of the oil-base drilling fluid tackifier at present, and has the advantages of favorable high temperature resistance, favorable tackifying performance and favorable environment friendliness.