The influences of the boiling point and fractional composition of coker gas oil (CGO) on the fluid catalytic cracking performance were investigated. Nitrogen compounds and condensed aromatics in CGO were identified by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography-mass spectrometry (GC-MS), respectively, and their effects were studied systematically. The result shows that the catalytic cracking performance of COO does not correspond to the boiling point of narrow fractions but rather to the basic nitrogen compounds and condensed aromatics that have high molecular weight and/or high condensation tendencies adversely. On the basis of these results, a divisional fluid catalytic cracking (DFCC) process was proposed where a separate reaction zone was added to reduce the contents and effects of the adverse compounds in CGO during catalytic cracking. The simulation experiments of the DFCC process show that improved conversion and enhanced yield of light oil can be achieved when an appropriate reaction condition is applied to every reaction zone.