Abstract: The amount of precipitated wax and its crystal morphology and structure, which are sensitive to thermal and shear history, are the key factors that govern the rheology of waxy crudes. The flowability improving of waxy crude is mainly based on modifying the morphology of wax crystal. In this paper, the microscopy characterization of wax crystal is summarized, the correlations are also discussed between wax crystal morphology and crude rheology with/without additives and before/after shear history. By applying a morphological method to extracting the wax crystal characters, comparisons of the different wax crystal images obtained from different experimental conditions are made, and the quantitative characters of wax crystal size and size distribution are achieved. It is demonstrated that the quantitative characters of crystal size and size distribution consist with the cognitions. This has laid a sound foundation for the further study of correlation between wax crystal structure and crude rheological properties.