The invention relates to a method for improving acrylonitrile device reaction yield, which mainly solves the problems that in the prior art, the reaction yield maintaining time is short; the production quantity of unwanted by-products such as the by-products containing carbonyl groups (acrolein and acrylic acid) is high, the by-products influence the device refined recovery, and a heat exchanger at a reactor outlet is easily blocked to result in increased device reaction pressure, high yield of COX and decreased selectivity of the acrylonitrile. The method adopts the technical scheme of removing 5 to 30 weight percent of acrylonitrile equilibrium catalyst from a bed layer of a fluidized bed reactor, adding an acrylonitrile regenerated catalyst into the bed layer of a fluidized bed to enable the quantity of the catalyst in the fluidized-bed reactor to be remained essentially the same, and performing normal operation under the original process conditions, so that the method for improving the acrylonitrile device reaction yield preferably solves the problems, and can be used in industrial devices for producing acrylonitrile and methacrylonitrile by adopting ammonia oxidation of isobutene and propylene.