This paper mainly studied charging and electric field characteristics of different proportions of biomass/coal co-combustion ashes (co-ash) in a self-designed high-voltage electrostatic field, including an evaluation of charging, volt-ampere and plate current density distribution characteristics of co-ash. In addition, the mechanisms that influenced charging and electric field characteristics were discussed by analyzing the morphology, chemical composition and specific resistance of co-ash. The research results showed that with an increase of biomass ratio in the co-combustion fuel, the charge-mass ratio of co-ash displayed a rising trend to a certain extent, and gradually enhanced particle-charging characteristics. The co-ash in an electric field manifested a property of being easier to charge, so a more optimal voltampere characteristic was obtained. Simultaneously, the results also indicated that the plate current density distribution of co-ash showed limited change with an increase of biomass ratio in co-combustion. (C) 2017 Elsevier Ltd. All rights reserved.