Carbon-coated Fe₃O₄ composites with firecracker-like structures have been fabricated by catalytic pyrolysis of polyamide (PA) in a sealed reaction system. As revealed in field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis, the diameter of the one-dimensional firecracker-like structures is about 4 μm and the diameter of the secondary nanorods is about 620 nm. The diameter of Fe₃O₄ nanorods inside the carbon shells is about 82 nm, and the thickness of the carbon shells is about 265 nm. Some important preparative parameters related to the synthesis have been identified and investigated by some designed experiments. The magnetic measurement at room temperature indicates that the values of saturation magnetization (19.2 emu g⁻¹) and coercivity (270.1 Oe) of the carbon-coated Fe₃O₄ composites with firecracker-like structures are different from those of Fe₃O₄ nanoparticles and bulk Fe₃O₄ due to the different carbon content, dipolar interaction, size and morphology of the products. The results also indicate that the one-dimensional Fe₃O₄@C core–shell structures possess good acid resistance.