The invention provides a dedusting apparatus for tail gas of a UO3-H2O system after dehydration and a dedusting method. UO3-H2O materials are dehydrated through a drying dehydration device, the majority of the dehydrated materials enters subsequent equipment, and the tail gas enters a tail gas inlet at the bottom of the dedusting apparatus from a tail gas outlet at the upper part of the drying dehydration device; in the dedusting apparatus, solid dust is adhered onto a filter pipe, and the tail gas id discharged from bottom to top via a tail gas outlet at the top of the dedusting apparatus; the discharged tail gas enters a hydration condenser for condensation, H2O enters a desalting water tank after condensation, NOx is converted into HNO3 and other acidic substances after meeting water, the acidic substances enter the desalting water tank together with H2O, and non-condensable gas enters a tail gas system through the hydration condenser. By using the dedusting apparatus, the tail gas generated during a technology process using a drying dehydration device can be effectively processed, condensed uranium-containing wastewater can be discharged through the desalting water tank or can be reused. The dedusting apparatus has the advantages of simple equipment structure, easiness for operation, easy availability of control conditions, good safety, and uniqueness and validity of the technology tail gas processing manner.