Abstract: Using brominated polystyrene (BPS) as flame retardant, Sb₂O₃ nanoparticles (nano-Sb₂O₃) as synergistic flame retardant, polybutylene terephthalate (PBT) as matrix and thermoplastic polyurethane elasticity (TPU) as a toughening component, TPU/nano-Sb₂O₃-BPS-PBT flame retardant composites were obtained by ball milling dispersion and melt-mixing methods. The mechanical and flame retardant properties of the TPU/nano-Sb₂O₃-BPS-PBT composites were studied by DSC, tensile, impact and limiting oxygen index (LOI) test. The results show that the TPU can enhance the toughness of the TPU/nano-Sb₂O₃-BPS-PBT flame retardant composites. With increasing of the mass fraction of TPU, the notched impact strength of the TPU/nano-Sb₂O₃-BPS-PBT flame retardant composites increases. Furthermore, when the mass fraction of TPU is 9wt%, its impact strength increases by 137% and the elongation at break increases by 340% compared with those of pure PBT, but its tensile strength decreases. The tensile strength of the composites is greater than that of pure PBT when the mass fraction of TPU is 3wt%, which its impact strength is 52% higher than that of the pure PBT. The TPU/nano-Sb₂O₃-BPS-PBT flame retardant composites reach flame-resistant grade and the composites show superior comprehensive performance.