People have long known how to improve the properties of wood by soaking and baking in water, and later learned to treat wood with tar, asphalt, tung oil, lacquer (see raw lacquer) or inorganic salts. These simple and effective treatments still exist among the people. In the 20th century, many modern wood modification technologies were developed. As early as in the early days, patents for making compressed wood have been published. Before World War II, Germany had already sold compressed wood products. During the period of 1930 ~ 1960, some new treatment methods appeared, such as hydroxyl acetylation, crosslinking reaction between cellulose and formaldehyde, cyanoethylation, addition of ethylene oxide and hydroxyl, ozonolysis, propiolactone grafting, polyethylene glycol and phenolic resin treatment. Wood treated with phenolic resin is called bakelite. Wood is impregnated with phenolic resin, then compressed, weighed, impregnated and pressed. In the late 1950s, plastic composite wood (WPC) appeared again. In recent ten years, people have focused on the research that various chemicals penetrate into the cell wall and react with hydroxyl groups, which not only achieves the effect of expanding wood and improving the dimensional stability of wood, but also changes the structure of wood polymer compounds, so that those microorganisms that cause wood decay cannot survive on new wood molecules, thus greatly improving the rot resistance of wood. Although there are many wood modification methods, up to now, due to the lack of technical or economic feasibility, most of the modification methods remain in the laboratory stage, and only compressed wood, impregnated wood, impregnated wood, polyethylene glycol treatment and plastic wood have different scales of industrial production. (Ou Yangming VIII)