In this work the cation effect of ion-exchanged y type Zeolite catalyst in the case of cracking and or isomerization reactions of n-pentane were investigated. Pure n-pentane was converted into various lower hydrocarbons under the conditions of below 2 atm, and 400℃ to 600℃ through isomerization and cracking reactions. According to a conventional method, the order of catalytic reactivity of the ion-exchanged catalysts for both reactions were confirmed as following ; i) Isomerization reactions, Cr^(++3)-y>Mg^(++)-y, Ca^(++)-y>Fe^(++)-y, Mn^(++)-y>Cd^(++)-y, Cu^(++)-y, Zn^(++)-y>Al^(+3), H^+-y, Mg^(++)-y, Co^(++)-y ii) Cracking, reactions Ni^(++)-y, Cd^(++)-y>Ca^(++)-y, Cr^(+3)-y, Zn^(++)-y, Mn^(++)-y>Fe^(++)-y Cu^(++)-y, Co^(++)y, Mg^(++)-y, H^+-y, Al^(+3)-y, Hg^(++)-y