Mineral compositions and microstructures of fluorine-bearing magnetite concentrate and vanadium-titanomagnetite concentrate are studied. The results show that a boride and a catalytic oxidation agent have great effects on ameliorating the mineral compositions and microstructures of these sinters, and the catalytic agent is more effective. Comparing these two kinds of ores, the performance of fluorine-bearing magnetite concentrate is better. Addition of 0.01% catalyst into fluorine-bearing magnetite concentrate can increase calcium ferrite content from 15%-20% up to 34%-39%, and its microstructure changes from large cavities and thin framework into intermediate cavities and thick framework, and the microcracks disappear.