Abstract: Several methods of characterizing the macroscopic size of heavy oil fractions are introduced. These methods mainly include hydrodynamic properties correlation method，small-angle scattering method and electron microscopy imaging method. The hydrodynamic properties correlation method is mainly used to compute the molecular size of heavy oil fractions，but the size and shape of asphaltene colloid particle are characterized by the small-angle scattering method and electron microscopy imaging method. The basic principle，condition of application and problem of these methods are also analyzed and summarized. Based on the analysis，the characterization methods of size，shape and distribution of asphaltene colloid particle are relatively mature，and the viscosity-diffusion coefficient combination method that investigates the hydrodynamic properties of heavy oil fractions in extremely dilute solution is a good way to characterize the molecular shape and size of heavy oil fractions，especially asphaltene.