VR (vacuum residua) and CCB oil (catalytic cracking bottom oil) are complex mixtures of hydrocarbons. The investigation of the compatibility and the incompatibility of them is helpful to optimize the ratio of CCB oil/VR in FCC processing and VR solvent deasphalting processing to prevent troubles. In the present work, the mixture property of VR with CCB oil was studied from the standpoint of colloidal dispersion in several different experiments. The investigation shows that in the course of CCB oil being blended with VR, there are two competitive processes of dissolution and flocculation, and the CCB oil's function is to act as both solvent and dispersant. At a low blending ratio of CCB oil, flocculation is almost balanced with dissolution; VR is almost compatible with CCB oil. When the blending ratio of CCB oil is increased, the solvation and dispersal powers of the CCB oil break through the tolerance limit of VR colloidal system, and flocculation predominates over dissolution, which leads to phase separation in the colloidal system and to deposition of the asphaltenes. Under this condition, VR is incompatible with CCB oil.