The invention belongs to the technical field of synthesis of organosilicon compound and particularly relates to a method for preparing phenyl trialkyl alkoxy silane by a nucleophilic method. Under inertia gas protection, the method includes adding sodium into methylbenzene and dispersant, heating and preparing metal sodium metallic particle suspension; adding metal sodium metallic particle suspension into mixed liquid of halogeno benzene and tetraalkoxy silane, then adding reaction accelerant, rectifying to obtain phenyl trialkyl alkoxy silane products after reaction mixture is subjected to solid-liquid separation; or adding halogeno benzene into the metal sodium metallic particle suspension to react to prepare phenyl alkali metal sodium salt suspension, adding the phenyl alkali metal sodium salt suspension into mixed liquid of tetraalkoxy silane and reaction accelerant, and rectifying to obtain phenyl trialkyl alkoxy silane products after reaction mixture is subjected to solid-liquid separation. The preparation conditions of normal pressure, low temperature, simple operation, mildness and controllability are achieved and industrialization is facilitated.