Polarity and compositional characterization of fractions separated from catalytic upgrading and thermal reaction samples were performed to elucidate their similarities and differences. The colloidal stability of residues presented an inflection point at the end of the coke-induction period during both catalytic and thermal upgrading, which reveals that the colloidal stability of the residue has an intrinsic relationship to its coking characteristics. The parameters affecting the colloidal stability of samples were elucidated, including fraction composition, mean molecular weight, and mean dipole moment. In comparison to the thermal reaction, the asphaltenes content during catalytic upgrading increased more slowly during the coke-induction period. The asphaltenes that were extracted from catalytic reaction samples had both less molecular weight (MW) and less polarity than that of the thermal reaction. The results proved that the catalyst and hydrogen restrained asphaltene condensation. For the two kinds of reactions, the dipole moment of asphaltenes increased during the coke-induction period and decreased with the reaction time going on after that, which reveals that asphaltenes having more polarity preferred to aggregate and transform into coke.