The mechanism of electrostatic charge generation is significant to understand relevant granular electrostatics occurred in granule handling systems. However, the knowledge about single granule charge generation is far from completion. In this work, electrostatic charge generation of single granule sliding along a metal plate was measured and the effects of normal stress in combination with the humidity, saturation and contact area on electrostatics generation were studied. It was found that the electrostatics generated in the process increased with normal stress, which was independent of granule material and humidity. Humidity decreased electrostatics generation but such effect was found to be reduced as the normal stress was increased. In this work, all sampled granules had almost the same increasing rate of electrostatics with time to reach the state of electrostatics saturation. Normal stress was found to be a significant factor effect on the contact area of granule-metal plate. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.