The invention discloses a preparation method of a polyvinylidene fluoride composite reinforced liquid separation film and aims to provide a preparation method of a film which has high mechanical property and high interception accuracy and from which a surface layer is stripped difficultly in a using process. The method comprises the following steps of: soaking a polyvinylidene fluoride liquid separation film or a polypropylene liquid separation film which is prepared by a thermally induced phase separation method and serves as a base film in any one of water and weakly polar organic liquid until film pores of the base film are filled with liquid; and coating polyvinylidene fluoride film casting liquid on the surface of the soaked base film and quickly soaking the base film in coagulating bath for curing so as to obtain the polyvinylidene fluoride composite reinforced liquid separation film. In the method, the polyvinylidene fluoride liquid separation film or the polypropylene liquid separation film which has high mechanical property and is obtained by the thermally induced phase separation method is taken as a reinforcing body, is soaked fully and is coated with the composite polyvinylidene fluoride film casting liquid, so that the obtained liquid separation film has high mechanical property and high interception accuracy.