Abstract: The hydrocracking tail oil of vacuum gas oil from Middle Eastern crude was cut into four narrow fractions. The catalytic cracking performance of fractions was tested in an advanced catalyst evaluation device (ACE). The hydrocarbon compositions of fractions and cracked products were analyzed by GC-MS. The results show that the content of saturates in the four fractions are all above 98.0%, and the content of paraffins increases while the content of naphthenes decreases with the cuts getting heavier, simultaneously, the paraffin and naphthene compounds shift toward the direction of high carbon numbers. The four fractions are prone to be cracked with high yields of LPG and gasoline and low yields of dry gas and coke. Under the same reaction conditions, as the fractions moving in the direction of high boiling point, the cracking ability increases, the yield of dry gas and coke decreases, the yield of LPG increases, the yield of gasoline increases with a slight loss in octane number, and the yield of diesel and heavy oil decreases.