The basic nitrogen compounds in coker gas oil (CGO) narrow fractions were enriched, and their influences on hydrocarbons during fluid catalytic cracking (FCC) were investigated. The results show that the content of basic nitrogen compounds has influence on hydrocarbons cracking during CGO FCC reaction, but it is not as obvious as reported before. Furthermore, the compositional and structural identification of basic extracts by positive-ion electrospray Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) shows that basic nitrogen compounds in CGO include N, N-2, NO, N2O1, and NS class species. The N-1 class species centered at 9 < DBE < 13 with a carbon number ranging from 20 to 24 is the most abundant, and it is a key for CGO's retarding performance. The effect of structure and composition of basic nitrogen compounds is much more obvious than that of content, and it is stronger with the increase of their rings plus double bond equivalence (DBE).