The pungent substance in pepper is capsaicin, in which capsaicin accounts for 69%, dihydrocapsaicin 22%, nordihydrocapsaicin 7%, homocapsaicin 1% and homodihydrocapsaicin 1%. Pure capsaicin is a monoclinic prism or a short flaky crystal with a melting point of 65℃, which produces irritating evaporation at high temperature. Capsaicin is soluble in ethanol, ether, benzene and alkaline aqueous solution, but insoluble in cold water. The content of capsaicin in pepper varies with varieties, generally 0.2-0.5%, but as long as its mass fraction reaches 1 mg/kg, it will make the taste feel obviously spicy. Volatiles in pepper were collected by water distillation and solvent extraction, and analyzed by GC-MS. It was proved that there were alcohol, hydroxyl compounds, pyrazine cyclic carbohydrates, resins and other components.