Electrostatic charge has been known to have great influence on the performance of dry powder inhalation (DPI) drug delivery. However our understanding on the electrostatic charge is still limited. The purpose of this work was to evaluate the role of electrostatic charge on the efficiency of drug emission and drug dispersion during inhalation drug delivery through a DPI. Salbutamol sulphate and inhalac 230 were chosen as model compounds, and the dry powder inhaler used was Rotahaler. A device for simultaneous measurements of electrostatic charge and aerosol aerodynamic diameter was developed in the current work. The accuracy of the measurement device was evaluated against an independent measurement using a Faraday Cage method. Aerosol emission efficiency, drug dispersion efficiency, and fine particle fraction (FPF) were characterized using a twin-stage-impinger (TSI) together with electrostatic charge characterization. The effect of electrostatic charge on the aerosol emission and drug dispersion was analyzed. It was found that electrostatic charge affected not only drug dispersion but also drug emission. The current study established a protocol for evaluating the role of electrostatic charge in the dry powder inhalation drug delivery, and could be useful for formulation and inhaler development.