The invention relates to a polycyclic aromatic hydrocarbon ring-opening catalyst and a preparation method thereof, and aims to mainly solve the problems of excessive ring opening of polycyclic aromatic hydrocarbon, low yield of monocyclic aromatic hydrocarbon, and high catalyst deactivation rate in the prior art. The technical scheme is that the catalyst provided by the invention comprises the following components in percentage by weight: 45-60.9% of at least one of FAU, BEA or MFI type zeolite, or amorphous silica-alumina, 10-30% of pseudo-boehmite, 0.1-0.5% of noble metal Pd, 3-6% of metal Co and 0.5-3% of at least one of Zn, Bi and Ni. By adopting the technical scheme, the problems are well solved. The polycyclic aromatic hydrocarbon ring-opening catalyst is suitable for the field of refining lightweight monocyclic aromatic hydrocarbon.