The effect of Cs content in Cs x H 3-x PW 12 O 40 on the catalytic performance of the reduced Ni-Cs x H 3-x PW 12 O 40 /Al 2 O 3 catalysts for hydrocracking of n-decane with the presence of thiophene and pyridine is studied. The catalysts were characterized by BET, XRD, in situ XRD, Raman, H 2 -TPR, H 2 -TPD, NH 3 -TPD and FT-IR of pyridine adsorption. The best result was obtained on 8%Ni-50%CsH 2 PW 12 O 40 /Al 2 O 3 catalyst which shows the highest catalytic activity and with tolerance to 525ppm of thiophene and 170ppm of pyridine (the reaction conditions: 2.0MPa, LHSV=2.92h −1 , H 2 /n-decane 1500 vol/vol at 300°C). The high catalytic performance of the catalyst may be due to the proper balance between metal and acid functions by adding a certain proportion of Cs to the system.