The invention relates to a novel method for efficiently synthesizing dibenzoylmethane. The product (dibenzoylmethane) is non-toxic, tasteless and widely used in PVC (polyvinyl chloride) plastics and ABS (acrylonitrile butadiene styrene) resins. The invention belongs to preparation of compounds containing C0 groups and only connecting carbon or hydrogen atoms, in particular relates to preparation of beta-dione. The method is characterized in that the dibenzoylmethane is prepared from methyl benzoate and acetophenone through a condensation reaction in an alkaline environment. The methyl benzoateis prepared from benzoic acid and methanol as raw materials and sulfuric acid as a catalyst through an esterification reaction. The main raw material, namely the methyl benzoate, of the target product, namely dibenzoylmethane, of the method, is prepared through a self-designed process, a catalyst, namely sodium methoxide, of the condensation reaction, is prepared according to the self-designed process, and technological conditions of the key steps of the condensation reaction for synthesizing the dibenzoylmethane are optimized. The invention provides the method for preparing the dibenzoylmethane with low raw material cost, a short condensation reaction period, few by-products, a high yield of dibenzoylmethane, complete solvent recovery and an excellent capability for improving photothermal stability of a thermoplastic resin. The condensation yield is 85%, and the crystallization yield is 95%.