Heavy oil could be classified into two parts: one is the easy cracking part, which is the main source of liquid hydrocarbon transportation fuels and industrial chemicals, and the other is the refractory cracking part, which is failed to be cracked by the present technologies and has negative effects on upgrading. Therefore, the efficient method to obtain a higher conversion of heavy oil is needed for the heavy oil processing industry. Coker gas oil (CGO), used as an example of heavy oil, is supposed to be hard to process during fluid catalytic cracking (FCC). The structural information in the molecular level of basic nitrogen compounds, nonbasic nitrogen compounds, and condensed aromatics in feedstock and liquid products from FCC was investigated. The coked catalysts in the catalytic cracking reaction of CGO were characterized. The results showed that these compounds, especially basic ones, are more difficult to crack, which are preferentially chemisorbed on the surface of the catalyst leading to less acid sites for other easy cracking hydrocarbons and the decrease of the activity of catalysts. Physical solvent removal and chemical catalytic adsorption were used to pretreat heavy oil, and the result indicated that either physical solvent removal or chemical catalytic adsorption is a good way to avoid the retarding effects of refractory cracking components, and better product distributions can be obtained.