Spherical nano-BaFe12O19 was prepared by Colloid template, layer-by-layer electrostatic self-assembly and heat treatment method. BaFe12O19/polyurethane (BF/PU) composite microspheres were prepared by Suspension in-situ polymerization. The Physical and chemical properties of the microspheres were analyzed by SEM, FTIR and TG-DSC, etc. The biocompatibility of microspheres was evaluated. Embolization experiments were performed in rete mirabile (RMB) of pigs. The results showed that BF/PU microspheres had a core-shell structure and good heat stability. The content of BaFe12O19 was 11.11wt% in microspheres. The density ofmicrospheres was 1.055g·cm-3, which was near to that of blood. The composite microspheres had agood biocompatibility and successfully embolized arteriovenous malformation (AVM) with different flow. BF/PU microspheres could be a new type of embolization material for cerebral AVM and has great potential as a therapeutic embolic agent.