Ordinary distillation has bubble and boiling phenomenon, while molecular distillation is the free evaporation on the surface of liquid film, with low operating pressure, generally 0.1-1pa order of magnitude and short heating time. Generally, it is only ten seconds to tens of seconds. The evaporation and condensation of ordinary distillation is a reversible process. There is a dynamic phase equilibrium between the liquid phase and the gas phase. In the process of molecular distillation, the molecules escaping from the heating surface fly directly to the condensation surface, and there is no possibility of returning to the heating surface in theory, so there is no substance that is difficult to separate in distillation. Distillation technology can separate the substances which are difficult to be separated by conventional distillation. The distillation device must ensure the high vacuum degree of the system pressure, have high requirements for the sealing of materials, and the distance between the evaporation surface and the condensation surface should be moderate. The processing of the equipment is difficult and the cost is high. The energy consumption of the product is small, because the whole distillation separation has less overheat loss, because of the unique structure of the molecular distillation device, the internal pressure is very low and the internal resistance is far smaller than the conventional distillation, so the energy consumption can be greatly saved.