dimethyl decadecane hydroxybutylammonium chloride is added to the reaction kettle, dichloromethane is added to dissolve, and after cooling to -30 ℃ under stirring, chlorosulfonic acid (theoretical amount) is added dropwise. After dropping, slowly raise the temperature to about 10 ℃ and stir for 1 h, then stir for 1 h at about 20 ℃, then cool to -30 ℃. Add cold methanol-sodium hydroxide aqueous solution and reflux for 1 h, let stand, wait for inorganic salt to precipitate and filter out, cool the filtrate to -30 ℃, and crystallize to obtain crude product. The crude product is recrystallized with ethanol to obtain a pure product.