The invention discloses a catalyst for mononuclear aromatics hydrogenation and conversion to light fractions. The catalyst comprises a carrier and metallic element supported on the carrier. The carrier is prepared according to the following step: a NaY molecular sieve is contacted with organic acid in an aqueous solvent so as to obtain a modified NaY molecular sieve, wherein a pore opening of the modified NaY molecular sieve is trumpet-shaped. As the pore opening of the molecular sieve carrier in the catalyst for mononuclear aromatics hydrogenation and conversion to light fractions is trumpet-shaped, probability of clogging is reduced, thus raising activity of the catalyst and prolonging service life of the catalyst. Therefore, the catalyst for mononuclear aromatics hydrogenation and conversion to light fractions has a good industrial application prospect.