[en] Cobalt ferrite hollow microspheres with protrusions/polythiophene (CFHMP/PTh) composites were successfully prepared by in-situ polymerization method of thiophene with CFHMP. The morphology, phase structure, thermal stability, static magnetic and electromagnetic parameters of samples were analyzed and characterized by scanning electron microscope (SEM), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR), thermogravimetric analysis (TG), vibrating sample magnetometer (VSM) and vector network analyzer (VNA). The results indicate that the saturation magnetization (Ms) and remnant magnetization (Mr) and coercivity (Hc) of CFHMP/PTh composites are 566.4 Oe, 40.8 emu/g and 17.6 emu/g, respectively. The dielectric property of CFHMP/PTh composites is better than that of CFHMP, but the magnetic property of CFHMP/PTh composites is worse than that of CFHMP. At the thickness of 3.0 mm CFHMP/PTh composites exhibit strong electromagnetic dissipation ability (R_L = −33.8 dB at 9.5 GHz) and the absorption bandwidth (R_L < −10 dB) is 3.1 GHz (8.2–11.3 GHz). - Highlights: • Cobalt ferrite hollow microspheres with protrusions/polythiophene composites were synthesized. • The morphology, electromagnetic parameter and reflection loss of composites were analyzed and measured. • The relationship between the reflection loss of absorbing material and its thickness was analyzed. • The composites exhibit excellent microwave absorption properties.