The invention discloses a method for recycling a metal oxide from a waste flue gas denitration catalyst, comprising the following steps of: crushing the waste flue gas denitration catalyst to carry out pre-roasting pretreatment at high temperature; adding Na2CO3 into the waste flue gas denitration catalyst according to the proportion, mixing, pulverizing and roasting at high temperature to obtain a sintering block; crushing the sintering block and putting the crushed sintering block into hot water, and stirring and lixiviating to obtain titanate; adding sulphuric acid into the titanate, filtering, water-washing and roasting to obtain TiO2; adding the sulphuric acid into the lixiviated filtering liquid to regulate a pH value to 8.0-9.0; adding excessive NH4Cl for vanadium precipitation; decomposing NH4VO3 obtained from filtering at high temperature to prepare a V2O5 product; adding hydrochloric acid into the filtering liquid subjected to the vanadium precipitation to regulate a pH value to 4.5-5.0; adding CaCl2 for molybdenum and tungsten precipitation; treating the CaM0O4 and CaWO4, obtained from filtering, with the hydrochloric acid and roasting to obtain MoO3 and WO3. The method of the invention has the advantages of simple process and apparatus, high recycling efficiency, good product technical data, large treatment capacity and the like.