The invention provides a Cs-VPO/SiO2 catalyst, a preparation method therefor and use of the Cs-VPO/SiO2 catalyst in preparation of acrylic acid through catalyzing condensation of acetic acid and trioxymethylene. The preparation method comprises the steps: (1) firstly, weighing vanadium pentoxide, adding the weighed vanadium pentoxide into a three-mouthed flask, then, adding isobutanol and benzyl alcohol into the three-mouthed flask, and carrying out constant-temperature stirring refluxing until the vanadium pentoxide is completely dissolved; and weighing phosphoric acid, slowly adding the weighed phosphoric acid into the flask, and then, continuing to carry out a constant-temperature refluxing reaction until the solution is dark blue, so as to obtain a vanadium-phosphorus oxide, i.e., VPO; and (2) adding SiO2 into the three-mouthed flask in the step (1), then, adding an aqueous solution of cesium carbonate into the three-mouthed flask, and carrying out a stirring reaction; and taking out a sample after the reaction is completed, carrying out suction filtration, carrying out washing with isobutanol and acetone, then, carrying out drying, grinding and roasting, tabletting the sample, and carrying out screening, thereby preparing the Cs-VPO/SiO2 catalyst. The Cs-VPO/SiO2 catalyst provided by the invention has the remarkable characteristic of having good catalytic activity and stability in a reaction process.