The invention discloses a method for preparing acetochlor. The method comprises a step of generating acetochlor, wherein a specific reaction of the step of generating the acetochlor comprises: enabling tertimide and ethyl alcohol to react to generate acetochlor and hydrogen chloride; and in the step of generating the acetochlor, the tertimide is dropwise added into the ethyl alcohol to mix with the ethyl alcohol. The method provided by the invention can increase the yield of producing the acetochlor by a methylene process.