Classification according to the dispersion system: according to the dispersion characteristics of the dosage form, that is, according to the dispersing medium in the state of the existence of the different state and the dispersed phase of the state of the dispersing media exist in different characteristics of the classification, the use of physical-chemical and other theories of the relevant issues for the study, basically reflecting the homogeneity of the form of the uniformity, stability, and the preparation of the method required. The main categories are: ① true solution: such as solution, syrup, glycerin, solution injection. ② colloidal solutions: such as solvents, gels. ③ Emulsions: such as oral emulsions, intravenous emulsions, creams and so on. ④ suspension: such as suspension lotion, oral suspension, part of the ointment. ⑤ Gas dispersion: such as aerosols, sprays and so on. (6) Solid dispersion: such as dispersions, pills, capsules, tablets and other common dosage forms. This kind of preparation occupies a large proportion in the drug preparation. ⑦ particulate class: drugs are usually dispersed in liquid or solid state with different sized particles, mainly characterized by the particle size is generally micron-level (such as microcapsules, microspheres, liposomes, etc.) or nanoscale (such as nano-capsules, nanoparticles, nano-liposomes, etc.).