The invention provides a method for prolonging the running period of an acrylic acid device. The method comprises the following steps: loading a catalyst without diluting by use of an inert filler, arranging coated catalyst bed layers having different heat resistances in a tube fixed-bed reactor according to the heat resistance in the axial direction of the reactor; and loading a coated catalyst relatively low in heat resistance in a position near the outlet of a reaction tube, and then orderly loading coated catalysts relatively high in heat resistance in such a manner that the coated catalyst close to the inlet of the reaction tube has the highest heat resistance, wherein the coated catalysts having different heat resistances are catalysts the inner cores of which are high-activity composite oxides with heat-resistant ceramic balls, and are obtained by controlling the sizes of the heat-resistant ceramic balls and the coating ratio of an active ingredient. Due to the adopted method, not only is the running period of the acrylic acid device prolonged, but also the production device has relatively high reaction efficiency.