The kinetic effect of hydrogen spillover activated ober 1^st Pt/Al₂O₃ reactor at 400℃ has been qualitatively investigeated in the following 2^nd HY zeolite reactor at 500℃. It was explained in the point of view that the spiltover hydrogen over Pt/Al₂O₃ might be the dominant factor to increase the hydrocracking reaction yiled of n-hexane.