Abstract: USY zeolite was modified by dealuminization with oxalic acid. The effects of oxalic acid amount used for the modification on the relative crystallinity, SiO₂/Al₂O₃ molar ratio, specific surface area, pore structure, acidity, and performance in decane hydrocracking of the resultant USY were investigated. The results showed that accompanying with the leaching of non-framework aluminum, some framework aluminum is also leached out from the modified USY zeolite; therefore, with the increase of the oxalic acid amount used, the SiO₂/Al₂O₃ ratio of the modified USY is increased, the acidic strength and acidic amount are decreased, while a maximal relative crystallinity is obtained at a moderate amount of oxalic acid. For the hydrocracking of decane over the USY zeolite modified by oxalic acid of 0.2 (mass ratio), the conversion of decane and the selectivity to primary cracking products are 68.5% and 80.1%, respectively. The high hydrocracking activity of the modified USY can be attributed to its mesoporous structure and abundant accessible acidic centers; moreover, the large pores is also favorable for the diffusion of primary cracking products to avoid secondary cracking, which may also enhance the selectivity of primary cracking products.