In this paper, we report a new method to prepare hollow carbonyl iron microspheres, which is called pitting corrosion method. The comparison of the morphology, specific surface area and apparent density of the initial and pitting corroded carbonyl iron microspheres demonstrate that the pitting corroded carbonyl iron has a hollow structure. The pitting corrosion process is uncovered through the concentration change of ferrous ion in the reaction solution and the TEM images with different pitting corrosion time. The formation mechanism of hollow microspheres via pitting corrosion is analyzed. Furthermore, this pitting corrosion method can also be used to prepare other hollow metal particles, such as Ni, Co, and Cu particles. The electromagnetic parameters of the samples before and after pitting corrosion are measured. The calculated reflection loss of the pitting corroded sample for single layer of 0.5 mm or 1.0 mm thickness at 2-18 GHz is much better than that of the initial one. The mechanism of the improvement of the microwave absorption properties is discussed. (c) 2013 Elsevier B.V. All rights reserved.