Abstract: Light hydrocarbon catalytic cracking has attracted much attention because of its low cracking temperature，adjustable product distribution and high propylene yield.A series of ZSM-5 catalysts modified with different metals were prepared by impregnation, and cracking performances of n-hexane over the modified ZSM-5 catalysts were evaluated in the continuous flow fixed-bed reactor. The results showed that the conversion of n-hexane was decreased by ZSM-5 catalysts modified with Ni，Fe，Cr and Co，respectively. The decreasing extent of the conversion of n-hexane was the largest after Co introduction, but the smaller after Fe and Cr introduction. Propylene and ethylene selectivity was different at the same conversion over ZSM-5 modified with different metals. Compared with other metal，Co introduction improved propylene selectivity in larger extent at low conversion of n-hexane. Therefore，in order to get high propylene selectivity，the conversion of n-hexane could be lowered by adding Co.

Key words: crack, ZSM-5 zeolite, modify with metal, n-hexane