The SrFe12O19@carbonyl iron (CI) core–shell composites used in microwave absorption are prepared by the metal–organic chemical vapor deposition (MOCVD). The x-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, and vector network analyzer are used to characterize the structural, electromagnetic, and absorption properties of the composites. The results show that the SrFe12O19@CI composites with a core–shell structure could be successfully prepared under the condition:deposition temperatures above 180?C, deposition time 30 min, and gas fl ow rate 30 mL/min. The electromagnetic properties of the composites change significantly, and their absorption capacities are improved. Of the obtained samples, those samples prepared at a deposition temperature of 180 ?C exhibit the best absorption performance. The refl ection loss of SrFe12O19@CI (180?C) with 1.5 mm–2.5 mm in thickness is less than?10 dB in a frequency range of 8 GHz–18 GHz, which covers the whole X band and Ku band.