In this manuscript, ultrastable Y (USY) zeolites are modified employing a liquid‐phase ion exchange method to furnish H‐USY with different properties. Modified with ammonium nitrate, H‐USY could largely improve the conversion in the alkylation reaction of benzene with cyclohexene due to the increase in Brunauer‐Emmett‐Teller (BET) specific surface area, Barrett‐Joyner‐Halenda (BJH) pore volume, BJH pore size, and acidity of H‐USY. Catalyzed by the molecular sieve modified twice with ammonium nitrate, this alkylation reaction demonstrated a 95.3 % conversion of cyclohexene with 97.4 % selectivity of cyclohexylbenzene. And we found that urea‐modified USY has the similar effect, a 96.1 % conversion of cyclohexene with slightly 94.9 % selectivity of cyclohexylbenzene.