The catalytic pyrolysis of heavy oils, gas oils, cracked diesel and gasoline fractions was investigated in a confined fluidized-bed reactor. The feed with a high H/C atomic ratio and low aromaticity showed good cracking performance, high feed conversion, and high yield and selectivity of total light olefins (i.e., ethene, propene, and butene). The cracked diesel and gasoline fractions with a low H/C atomic ratio and high aromaticity showed poor secondary cracking performance. A characterization parameter (K-CP) was proposed to characterize the cracking performance of various feedstocks. The yield of total light olefins increased with an increase in K-CP, despite the catalytic or thermal pyrolysis. K-CP could be used as a criterion to evaluate the cracking performance of a feed for the production of light olefins. The cracking performance of a feed was considered desirable for K-CP above 3.6 and undesirable for K-CP below 2.8. Besides K-CP, the, United States Bureau of Mineral Correlation Index (BMCI) was also suitable to characterize the cracking performance of various feed for catalytic pyrolysis.