Based on the material composition and distribution of asphalt mixtures， scanning electron microscopy （SEM） was used to determine the thickness of the asphalt film wrapped around the aggregate surface in hot mix asphalt mixtures， and to propose a mixing workability evaluation index. Then the changes of mixing workability in different hot mix asphalt mixtures were further verified and analyzed through the index of aggregate distribution and compaction. The results show that the type of asphalt， gradation type， and mixing temperature have different effects on the mixing workability of hot mix asphalt mixtures. The better the uniformity of asphalt film attachment to the aggregate surface， the better the mixing workability of hot mix asphalt mixtures， the less discrete the aggregate distribution， the greater the compaction of the hot mix asphalt mixtures molding.