The acidity of bifunctional catalysts is regarded as one of the most important factors for FCC gasoline hydrotreatment. To investigate the effects of acidity on catalytic performance, the CoMo/Al2O3 catalysts modified by MCM-41 and HZSM-5 were prepared by incipient wetness impregnation. The characterization results showed that adding molecular sieves changed the distribution of acid sites of catalysts and had a positive impact on forming longer MoS2 slabs with a slightly higher stacking number related to better hydrodesulfurization (HDS) performance. The results of catalytic performance indicated that 1-octene isomerization conversion increased from 4.13 to 33.97% with the increasing Bronsted acid site/Lewis acid site (BAS/Lewis acid sites (LAS)) ratio by presenting stronger BAS, resulting in the increasing selectivity of hydrodesulfurization/olefin hydrogenation (HDS/HYDO) from 0.89 to 5.41. However, when the BAS/LAS ratio surpassed 0.46 with the presence of weaker and stronger BAS, HDS efficiencies started decreasing. This understanding sheds light on designing hydrotreating catalysts to produce high-quality gasoline.