An antimony trioxide purification method is disclosed by the invention. Firstly industrial grade antimony trioxide and acetic acid water solution are added into a stainless steel high-pressure reactorwith a stirring and cooling device, nitrogen is used for replacing air in the kettle, the reaction product is heated to enable the temperature of the reaction product to rise to 130-170 DEG C, and acorresponding pressure of 0.2-0.7 MPa is generated, the stirring is kept for 1-8 hours, and the materials are cooled to normal pressure at normal temperature, stirring is continuously carried out for0.5-2 hours to carry out a hydrolysis reaction, and the material is removed after the hydrolysis reaction is completed, and reduced pressure suction filtration is carried out, the filtrate is removed,and the filtered solid is washed with hot water to be neutral to obtain the wet antimony trioxide, then the wet antimony trioxide is put into a dryer to be dried to obtain the antimony trioxide product, wherein the quality index of the obtained antimony trioxide product reaches the standard of a national standard chemical reagent.