The invention discloses a nine-core gold cluster compound and a synthesis method thereof, relates to a gold cluster compound, and provides the nine-core gold cluster compound which is higher in stability and capable of emitting strong light in a liquid state, as well as a synthesis method thereof. The molecular formula of the nine-core gold cluster compound is [Au9(PC17NH13)6](BF4)3. The synthesis method comprises the following steps: mixing diphenylphosphine and butyl lithium in tetrahydrofuran to obtain a solution A; dissolving 2,6-dichloropyridine in tetrahydrofuran, and adding into the solution A; pumping out the solvent, adding water for carrying out quenching reaction, using dichloromethane to extract, collecting an organic layer, separating by a silicagel column to obtain 2,6-diphenyl phosphino-pyridine; dissolving in dichloromethane, adding Me2SAuCl, stirring, adding AgBF4, filtering, removing the solvent to obtain a compound [(PNP)2Au2](BF4)2; dissolving the compound [(PNP)2Au2](BF4)2 in dichloromethane, and adding a methanol solution which is dissolved with KOH and NaBF4, removing the solvent after refluxing, and extracting by dichloromethane to obtain the nine-core gold cluster compound.