A method for preparing a light olefin using an oxygen-containing compound, comprising the following steps: step a) in which a raw material comprising the oxygen-containing compound is introduced in parallel from n feeding branch lines into 1 st to n th secondary reaction zones in a dense phase fluidized bed reactor, and is brought into contact with a catalyst to generate a light olefin product-containing stream and a spent catalyst, wherein said catalyst is sequentially passed through 1 st to n th secondary reaction zones, with the carbon content thereof increasing gradually, and wherein said dense phase fluidized bed reactor is divided by a material flow controller into n secondary reaction zones; step b) in which the light olefin product-containing stream flowed out from the 1 st to n th secondary reaction zones is separated from the spent catalyst that it carries; said light olefin product-containing stream is passed into a product separation section, and after separation and purification, a light olefin product is obtained; the isolated spent catalyst is passed into the n th secondary reaction zone; and step c) in which the spent catalyst flowed out from the n th secondary reaction zone, after being stripped and lifted, is passed into a dense phase fluidized bed regenerator for regeneration; said spent catalyst is sequentially passed through 1 st to m th secondary regeneration zones; a regeneration medium is introduced in parallel from m feeding branch lines of regeneration zone into the 1 st to m th secondary regeneration zones; the spent catalyst is brought into contact with the regeneration medium, with the carbon content thereof decreasing gradually; after the completion of the regeneration, the catalyst is returned back to the 1 st secondary reaction zone via stripping and lifting; wherein the dense phase fluidized bed regenerator is divided by a material flow controller into m secondary regeneration zones; wherein n≥2 and m≥2. step a) in which a raw material comprising the oxygen-containing compound is introduced in parallel from n feeding branch lines into 1 st to n th secondary reaction zones in a dense phase fluidized bed reactor, and is brought into contact with a catalyst to generate a light olefin product-containing stream and a spent catalyst, wherein said catalyst is sequentially passed through 1 st to n th secondary reaction zones, with the carbon content thereof increasing gradually, and wherein said dense phase fluidized bed reactor is divided by a material flow controller into n secondary reaction zones; step b) in which the light olefin product-containing stream flowed out from the 1 st to n th secondary reaction zones is separated from the spent catalyst that it carries; said light olefin product-containing stream is passed into a product separation section, and after separation and purification, a light olefin product is obtained; the isolated spent catalyst is passed into the n th secondary reaction zone; and step c) in which the spent catalyst flowed out from the n th secondary reaction zone, after being stripped and lifted, is passed into a dense phase fluidized bed regenerator for regeneration; said spent catalyst is sequentially passed through 1 st to m th secondary regeneration zones; a regeneration medium is introduced in parallel from m feeding branch lines of regeneration zone into the 1 st to m th secondary regeneration zones; the spent catalyst is brought into contact with the regeneration medium, with the carbon content thereof decreasing gradually; after the completion of the regeneration, the catalyst is returned back to the 1 st secondary reaction zone via stripping and lifting; wherein the dense phase fluidized bed regenerator is divided by a material flow controller into m secondary regeneration zones; wherein n≥2 and m≥2.