The present invention discloses a process for the ammoximation of carbonyl compounds, wherein a reaction in a liquid reaction system comprising a carbonyl compound, ammonia and hydrogen peroxide is carried out in the presence of a sillicon-containing catalyst, characterized in that a liquid silicon-containing assistant is added to the reaction system so that the silicon concentration in the system reaches a range of between 0.1 and 10000 ppm. In the process according to the present invention, the deactivation of catalyst due to dissolution of silicon in the catalyst can be reduced, thus lifetime of the catalyst extended and the stable operation time elongated.