Abstract: The present invention relates to a ?-[2-(polyalkyleneoxy)ethylthio]alkylalkoxysilane derivative and a preparation method thereof, more particularly to a ?-[2-(polyalkyleneoxy)ethylthio]alkylalkoxysilane derivative prepared by transforming a (?-mercaptoalkyl)alkylalkoxysilane compound into a ?-(alkoxysilyl)alkylthiolate metal salt by treating it with a metallic base and performing dehalometallation at low reaction temperature using a poly(alkyleneoxy)alkyl ether halide or a poly(alkyleneoxy)bis(haloalkyl) ether to form a carbon-sulfur bond and a preparation method thereof. The novel compound of the present invention has not only a Si—OR bond but also contains a sulfur atom in the molecule, so that it can be used as monomer for synthesizing hydrophilic functional silicon polymers, source material of silicon-based surfactants and surface modifier of organic/inorganic materials.