In a method of preparing cyanoalkyl-akoxysilanes, which is suitable for the production of these silanes on a large technical scale, the reaction of a chloroalkyl-alkoxysilane with an alkali metal cyanide in the presence of a solvent takes place in a stirring reactor which is provided with means for loading these starting materials and with an outlet opening for the alkali metal chloride by-product, and which is connected through a bypass valve to a column with a superimposed condenser. After the reaction in the reactor has ended, first the solvent is distilled out through the column and then the main part of the cyanosilane, and then the rest of the cyanosilane is distilled out while bypassing the column. The alkali metal chloride is then removed from the reactor through a lock.