Variable charge molecular dynamics simulations of SiC intergranular glassy films have been performed based on the iterative fluctuation charge model. The atomistic structures of different configurations of the intergranular films are simulated. Charge transfer between the films and their neighboring crystals is observed and the equilibrium film thickness is found to be dependent on the charge transfer. Our results provide a direct proof for the existence of space charges and show that electrostatic interaction contributes to the equilibrium thickness of the intergranular films.