As a kind of transdermal drug delivery systems, external therapy can avoid first pass effect, It also has an advantage of releasing medicament steadily and direct acting on body surface,skeleton and muscle. As a common external therapy, plasters have complicated ingredients. The elements in plasters also absorb into the body in a different way from oral drug. How to make more drug penetrate through the skin as well as test the elements and concentrations that enter the body are still the main problems that quality control of plasters facing. The article summarizes the history of external therapy, particularly the plasters. Based on the researches in recent years, the article generalizes the penetration enhancers and methods which can promote the penetration rate and the way to detect the penetrate rate. The author introduces the advantages and usages of plasters in neurodegenerative diseases and hopes to provide brand new thinking that can help to improve the productions and uses of plasters.