The invention discloses a p-phenyl substituted alpha-diimine palladium catalyst and a preparation method thereof. The preparation method comprises the following steps: adding a p-phenyl substituted aniline derivative and 2,3-butanedione into a dry flask, carrying out a reflux reaction by taking absolute methanol as a solvent and formic acid as a catalyst to obtain a precipitate, recrystallizing the obtained crude product through a mixed solvent, carrying out filtering, carrying out washing with cold ethanol, and carrying out vacuum drying to obtain a p-phenyl substituted alpha-diimine ligand;and under protection of N2, mixing the p-phenyl substituted alpha-diimine ligand with PdCl2(MeCN)2, adding CH2Cl2, carrying out stirring for reacting, filtering the mixed solution, removing the solvent of the obtained liquid by rotary evaporation, washing the obtained solid with diethyl ether, and finally carrying out vacuum drying to obtain the catalyst. The catalyst disclosed by the invention isapplied to an alpha-olefin polymerization reaction, and polyalpha-olefin (PAO) lubricating oil base oil obtained through a polymer has the advantages of low pour point, high viscosity index and the like, so that the use effect of PAO lubricating oil is greatly improved, and use requirements on the market are met.