The invention discloses a method for preparing calcium carbonate filler by using composite modifier. The method comprises the steps of: first taking sodium oleate and deionized water, preparing a sodium oleate aqueous solution, mixing the sodium oleate aqueous solution with calcium carbonate powder, performing stirring, then keeping the mixture standing, performing suction filtration, washing thecalcium carbonate obtained after suction filtration by using deionized water, performing drying, then adding the dried calcium carbonate powder into water, and performing mixing to form suspension; adding a vegetable acid-type mono-alkoxy titanate coupling agent and a vinyl octadecyl silicate coupling agent sequentially, performing stirring, then adding cyclohexyl-1,2-diisononyl dicarboxylate plasticizer, performing heating after stirring is conducted, then adding stearic acid, performing even stirring, adding maleic anhydride grafted compatibilizer and ascorbic acid under a heating condition,performing even stirring, keeping the mixture standing after a reaction is completed, performing suction filtration, performing high-temperature drying on the calcium carbonate obtained after suctionfiltration, and performing cooling to obtain the modified calcium carbonate filler. The method for preparing the calcium carbonate filler by using the composite modifier has a simple preparation process, a short process and a good application prospect.