Provided in the present invention is a preparation method for a phosphonic salt, comprising the step of: reacting 3,7,11-trimethyldodec-1,4,6,10-tetraene-3-ol with triarylphosphine and an acid in an alcohol solvent at 50-100°C to form the phosphonic salt, wherein the acid is a sulfamic acid or methanesulfonic acid, and the alcohol solvent is a straight chain monohydric alcohol containing 1-5 carbon atoms. The method is performed in nearly neutral conditions, greatly reducing the generation of impurities and greatly obtaining phosphonic salt with an increased E content. The yield of lycopene obtained by using the phosphonic salt as a raw material is high.