The invention discloses a preparation method of methyl ketone oxime methoxy silane. The method comprises the following steps: (1), adding butanone oxime, methanol and miscella No. 120 into a reaction kettle with a stirring function, then dripping methyl trichlorosilane into the reaction kettle, adjusting dripping speed of the methyl trichlorosilane, and controlling the reaction temperature between 30 DEG C and 60 DEG C; (2), after the dripping is completed, performing still standing for layering, adding an upper-layer product into a first neutralization kettle, pumping ammonia gas for neutralization, then filtering, separating ammonium chloride, and distilling out miscella to obtain a product; adding a lower-layer product into a second neutralization kettle, adding the miscella, pumping ammonia gas for neutralization, then filtering, separating ammonium chloride, and distilling out the No. 120 miscella to obtain the butanone oxime. The method provided by the invention is simple, feasible, suitable for industrial production, high in product yield and low in manufacturing cost; the prepared product has excellent activation, can be used for preparing RTV silicone rubber which meets fast surface dry requirements, and has low possibility of discoloration during storage.