Abstract: A fluidized-bed catalyst for producing acrylonitrile by the ammoxidation of propylene, which comprises a silica carrier and a composite having the following formula: AaCcDdNafFegBihMiMo12Ox wherein A selected from the group consisting of potassium, rubidium, cesium, samarium, thallium and mixtures thereof; C is selected from the group consisting of phosphorus, arsenic, boron, antimony, chromium and mixtures thereof; D is selected from nickel, cobalt or mixtures thereof; M is selected from tungsten, vanadium or mixtures thereof. The catalyst of the present invention particularly suits the use under higher pressure and higher duties, and still maintains very high single-pass yield of acrylonitrile and a high ammonia conversion. This catalyst particularly suits the requirement for existing acrylonitrile plants to raise capacity. For new plants it can also reduce the investment on the catalyst and the pollution.