Low-emissivity Au thin films were sputter-deposited on three groups of nickel alloy substrates with different surface roughness for high-temperature application. After deposition, the samples were heated in air at 600 degrees C for 200 h to simulate the application environment. The results showed that the substrate roughness had great influences on infrared-emissivity characteristics of the Au films. The average infrared emissivity of the samples with small roughness just increased a little after heat treatment, while it greatly increased for the sample with large roughness. Increasing the roughness of the samples will not only increase the effective surface emitting area, but also become a detriment to the integrity of Au films. (C) 2010 Elsevier B.V. All rights reserved.