The invention discloses a method and system for preparing methyl heptenone, and solves the problems of long reaction time, high reaction temperature and low yield in the preparation of the methyl heptenone in the prior art. According to the method for preparing the methyl heptenone, which is disclosed by the invention, methyl butenol and methyl acetoacetate are used as raw materials, diazabicycloand aluminium isopropoxide are used as catalysts, and a reaction is performed to prepare the methyl heptenone. The system for preparing the methyl heptenone, which is disclosed by the invention, comprises a one-step reaction still, a second-step reaction still, a first rectifying tower, a second rectifying tower, a carbon dioxide collecting tank, a methanol collecting tank and a methyl heptenone collecting tank. The method and the system disclosed by the invention have the advantages of simple process and simple and convenient operation; Carroll reaction time can be effectively shortened; yield of a finished product can be effectively improved; a reaction temperature is low.