To provide a method for producing the subject compound by reacting a preheated fatty alcohol with an alkyl glycoside at a given pressure, and flash drying the effluent to remove the alcohol products, so as to avoid excessive heating and thereby to prevent coloring and thermal cracking of the subject compound.

This method produces an 8-20C alkyl glycoside by the glycoside exchange reaction between a 2-6C alkyl glycoside and 8-20C fatty alcohol in the presence of an acidic catalyst, wherein the 8-20C fatty alcohol preheated at least to 80°C is mixed with and then reacted with the 2-6C alkyl glycoside at 1.1 to 10 bar and 60 to 140°C, preferably 80 to 120°C in the presence of an acidic catalyst (e.g. p-toluenesulfonate), and the effluent is flash-dried under a vacuum of 1 to 700 mbar, preferably 3 to 40 mbar to remove the 2-6C alcohol products, to efficiently produce the subject compound while avoiding excessive heating by jacket temperature and thereby preventing coloring and thermal cracking of the compound.