Doped-polypyrrole/Fe₃O₄ (D-PPy/Fe₃O₄) nanospheres were successfully synthesized via a onepot process. In this process, polyvinyl alcohol (PVA) plays an important role in the construction of polypyrrole nanoparticles, and Fe3+ ions were the oxidant and the only raw resource of Fe₃O₄. The morphology, magnetic properties, and electromagnetic microwave absorption properties of D-PPy/Fe₃O₄ composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), a vibrating sample magnetometer (VSM) and a vector network analyser (VNA). The results indicate that D-PPy/Fe₃O₄ nanospheres become more disperse and regular due to the addition of PVA. The influence of the mass ratio of PVA to pyrrole on the microwave absorption performance of the D-PPy/Fe₃O₄ composites was also investigated. When the mass ratio of PVA/pyrrole was 0.75:1, the minimum reflection loss (RLmin) value of the D-PPy/Fe₃O₄ composites reached -41.3 dB at 7.7 GHz with a thickness of 3.0 mm. The microwave interference cancellation of interface reflection, nature resonance loss and current loss are the main reasons for the loss of electromagnetic microwaves for the as-prepared D-PPy/Fe₃O₄ composites.