Abstract: Heavy oil is an extremely complex colloidal system. In order to research the colloidal structure of heavy oil and its structure variation by change of external conditions such as temperature and shearing rate. Ten kinds of model compounds were chosen to represent the composition of heavy oil. Dissipative particle dynamics (DPD) was applied to simulate the changes of colloidal structure of heavy oil at different temperature and different shearing rate. The simulation results show that heavy oil possesses a colloidal structure made of components and that the polarity of the colloidal structure becomes gradually weaken from inside to outside. The dispersed phase is colloidal particle and the continuous phase is saturates and mononuclear aromatic. The heavy oil colloidal activation is greatly influenced by temperature. At certain temperature the heavy oil colloidal will has a most suitable activation status. Shear viscosity of heavy oil reduces with the increase of the shearing rate. Heavy oil exhibits the characteristics of pseudoplastic fluid.