Abstract: The major chemical composition, mineral composition, element distribution rate and mineral dissemination features of harmful elements in mixed raw ore of Bayan Obo were studied by means of multi-element chemical analysis, automatic mineral analysis system, partial reflection microscope, field emission scanning electron microscope and energy spectrometer. The results shows that the content of harmful elements in Bayan Obo mixed raw ore is relatively high, with P₂O₅ being 2.98%, F 8.89% and S 1.63% respectively. The harmful elements in mixed raw ore mainly exist in the form of independent minerals, including fluorite, bastnasite, monazite, apatite, barite, pyrite, etc., and the element distribution rate is above 93%. The minerals containing harmful elements in the mixed raw ore are widely distributed in the mining area, with diverse morphology and occurrence, small size of useful minerals, complex symbiotic association and contact relationship of minerals, which have a great impact on the production of high-quality products. The research results provides a theoretical basis for the upgrading of the ore production process in the future.