Gadolinium oxide, with the chemical formula Gd2O3, is prepared from monazite or mixed rare earth minerals through extraction and purification steps to obtain a mixed rare earth solution of samarium and gadolinium. Gadolinium oxalate is precipitated with oxalic acid, and then separated, dried, and burned to obtain gadolinium oxide. Preparation method: After purification steps such as extraction, a mixed rare earth solution of samarium gadolinium is prepared. Precipitate gadolinium oxalate with oxalic acid, separate, dry, and burn to obtain gadolinium oxide