The effect of oxidation roasting on the surface characteristics and flotation behavior of bastnaesite was investigated. Oxidation roasting experiments were performed at various temperatures, time, and O₂ concentrations. The results indicated that increasing the temperature promoted the thermal decomposition of bastnaesite, resulting in the formation of Ce₇O₁₂, RE₂O₃, and REF₃ as the main phases. Furthermore, oxidation roasting induced the formation of long, narrow, and nearly parallel cracks within the particles, increasing the porosity and facilitating partial particle fragmentation. During flotation, the concentration of dissolved rare earth ions increased significantly, and surface hydrolysis led to the formation of rare earth hydroxyl compounds. The complete decomposition of bastnaesite increased the required collector dosage to achieve a recovery above 85.00%. This increase might be attributed to the enhanced particle wettability, the altered adsorption mechanism of the collector, and the deeper penetration of the collector into the porous structure.