Thermal barrier coatings (TBCs) are not the pure bulk materials, and they contain many different micro/nano structures caused by the plasma spraying process. The microstructures in the coatings play a very important role on mechanical and thermal properties, therefore, the coating properties differ hugely from those of the corresponding bulk materials. The influence of microstructures on thermal conductivity has been investigated by many researchers, however their effect on radiative heat transfer is seldom studied. The radiative heat transfer will become increasingly important as the temperature rises, and this warrants the study on the influence of microstructures on radiative properties. In the present paper, Finite-Difference-Time-Domain (FDTD) method was employed to simulate the radiative heat transfer behaviors of TBCs with different types of microstructures. The relationship between microstructures and radiative properties of the coating is investigated. Furthermore, the parameters of microstructures such as defect size, shape coefficient, porosity and orientation angle are examined in detail. The results will help us to further understand the radiative heat transfer process across the TBCs and will provide us a theoretical guide to design TBCs with a high thermal insulation property. (C) 2014 Elsevier Ltd. All rights reserved.