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Epoxy used as insulating material in electronic and electrical devices plays an important role in system reliability. Addition of nanoparticles into epoxy can improve the insulating properties compared with undoped material. However, due to the change of the material structure, trap characteristics and charge behaviors are altered as a consequence. This possibly leads to distortion of electric field that can result in degradation of the insulation. From the viewpoint of safety, it is necessary to investigate charge behavior of epoxy nanocomposites. This paper presents study aimed at clarifying the effect of nano-filler concentration on surface charge accumulation and decay behaviors of epoxy/TiO2 nanocomposites. Samples were prepared by dispersing nano-scale TiO2 into epoxy by mixing with shear force. Corona charging tests were performed at room temperature with a relative humidity of ~ 40%. The charge distribution was measured by means of an electrostatic voltmeter. Obtained results show the dependence of the charge density as well as the charge decay rate upon the concentration of TiO2, varying as a function of the charge polarity, charging time and charging voltage. It is suggested that the charge dynamics is dependent upon the characteristics of localized surface states that are altered by the nanoparticles.