The linkages between coking characteristics, colloidal stability, and molecular characteristics of petroleum residue during thermal reaction were studied. First, the results reveal that the colloidal stability decreases sharply during the coke- induction period and changes little after that. This observation proves that the colloidal stability variation determines the coking characteristics of residue. Second, the asphaltene concentration increases as reaction time progresses, reaches its maximum at the end of the coke- induction period, and then declines thereafter. This result reveals that asphaltene aggregation happens when the colloidal stability of the residue decreases to its limit and that the aggregated asphaltenes will transform into coke to abate the worsening of the colloidal stability. Furthermore, the variation in fraction composition shows that the saturated solubility of asphaltenes in residue decreases as the reaction goes on after the coke- induction period. Moreover, both the VPO molecular- weight value and the mean dipole- moment value of asphaltenes show maxima at the end of the coke-induction period, which reveals that asphaltenes with larger MW values and more polarity prefer to aggregate and transform into coke.