The invention belongs to the field of modified silicone oil, specifically relates to a preparation method of alkoxy end capping silicone oil, and aims at solving the technical problems of the existing preparation that the process is complex because of starting from chlorosilane monomer, hydrogen chloride produced by hydrolyzing is difficult to remove, and therefore, the storage stability of a product is poor. The preparation method of the alkoxy end capping silicone oil comprises the following steps: adding a catalyst to high-viscosity-end hydroxyl polydimethylsiloxane and alkoxy silane under the protection of nitrogen, heating to be 80 to 130 DEG C, and reacting for 1 to 6 hours; b, neutralizing to be neutral after the reaction is done; c, filtering to obtain the filtrate that is the crude alkoxy end capping silicone oil product; d, distilling the crude product under a temperature of 120 to 170 DEG C and at a pressure of -0.06 to -0.09Mpa to obtain the alkoxy end capping silicone oil. According to the preparation method of the alkoxy end capping silicone oil, the reaction line is simple, the alkoxy end capping silicone oil is high in stability and high in end capping rate, and a new method is provided to the preparation of the alkoxy end capping silicone oil.