The invention relates to a method for synthesizing phenanthrene compounds shown in the formula (I) in the specification from palladium acetylacetonate. The method comprises steps as follows: a compound in the formula (II) and a compound in the formula (III) are subjected to a reaction in a solvent in an inert atmosphere in the presence of a catalyst containing palladium acetylacetonate, an organic ligand and alkali, and the compound in the formula (I) in the specification is obtained, wherein each of R1 and R2 is independently H, C1-C6 alkyl groups, C1-C6 alkoxy groups or halogens, R3 is C6-C10 aryl groups or C5-C8 heteroaryl, C6-C10 aryl groups or C4-C8 heteroaryl are optionally substituted by 1-3 substituent groups, and the substituent groups are C1-C6 alkyl groups or halogens. The method has a good effect through proper selection of the catalyst, the organic ligand, alkali and the solvent and has wide industrial application prospect.