The invention relates to a method for preparing a topological insulator Bi2Se3 (bismuth selenide) and perovskite oxide La0.7Sr0.3MnO3 composite structure. The method comprises the following steps of a, measuring, grinding and tabletting bismuth powder and selenium powder in an argon glove box according to a molar ratio of 2:3, sealing the bismuth powder and selenium powder into a vacuum quartz tube, and then sintering and quenching the bismuth powder and selenium powder to prepare Bi2Se3 single crystal wafers; b, dissolving lanthana, strontium carbonate and manganese acetate into a nitric acid solution according to a molar ratio of 7:3:10, adding a complexing agent, and placing the mixture into a furnace to be sintered to obtain La0.7Sr0.3MnO3 precursor powder; c, mixing the prepared precursor powder with a little silane coupling agent; d, adding silicone rubber into the precursor powder obtained in step c, uniformly mixing the silicone rubber and the precursor power, and tabletting the mixture; e, laminating the substrate obtained in step d with the Bi2Se3 single crystal wafers, pressurizing and solidifying the laminated substrate, and then stripping the Bi2Se3 single crystal wafers by utilizing an adhesive tape. The preparation process of the method is simple, the preparation period is short, easiness in operation can be realized, and the preparation cost is greatly reduced.