The application of suspension magnetization roasting technology in ferruginous rare earth bearing orehas gained significant attention. Bastnaesite, due to its pyrolysis characteristics, has been proposed asa reductant for iron minerals. In this study, the pyrolysis of bastnaesite was investigated through variousin-situ methods. The results showed that during pyrolysis, CeOF and CO2 were first generated, followedby the reaction of CO2 with Ce2O3 and Ce7O12 to produce CO. Pyrolysis occurred initially on the particlesurface and then progressed inward. Increasing the roasting temperature promoted the pyrolysis of bastnaesiteand CO generation. The addition of CO2 during the roasting process enhanced the formation of CO. The pyrolysis kinetic mechanisms under isothermal and non-isothermal conditions were phaseboundarycontrolled reaction mechanism (n = 4) and phase-boundary controlled reaction mechanism(n = 2–4), respectively. This detailed analysis of the pyrolysis behavior of bastnaesite facilitates the efficientand low-carbon development of ferruginous rare earth ores through suspension magnetizationroasting.