The invention relates to the field of catalysis, in particular to a method for preparing aryl ketone through reacting aldehyde with aryl boric acid under the catalysis of a ruthenium catalyst. In the method, an organic phosphide is used as a ligand, potassium phosphate is used as alkali, pinacolone or acetone is used as an additive, toluene or/and water is (are) used as a solvent(s), aldehyde and aryl boric acid which are used as reaction substrates react at 95-100 DEG C for 10-24h in the presence of a ruthenium compound used as a catalyst to prepare aryl ketone, wherein the catalyst is one of [Ru(cymene)Cl2]2, [Ru(CO)3Cl2]2, RuH2(CO)PPh3, Ru2(OAc)4, [Ru(benzene)Cl2]2, Ru(S-BINAP)Cl2 or Ru3(CO)12. In the invention, the used catalyst has relatively low price and low toxicity, thereby reducing the preparation cost and being more environmentally friendly.