The inanition provides a falling film continuous preparation method of acyloxysilane. According to the invention, chlorosilane and glacial acetic acid are delivered through a heated graphite falling film evaporator set, and are subjected to a reaction in a manner of liquid film; produced HCl gas is evaporated fast from the film. Therefore, side reactions caused by HCl retained in the system and thermal decomposition caused by long-period high temperature are avoided, and high-yield and high-quality acyloxysilane can be prepared under a condition with low temperature and no solvent.