A magnetic single-component development process in electrophotography has interesting characteristics on a magnetic and electrostatic interaction of toner particles. Magnetic force restrains toner adhesion to non-image area and this feature enhances the development. However, long chains made by magnetic interaction force between magnetic toner particles deteriorate toner-image quality on the photoreceptor. It is known from a past experimental study that the magnetic chain length is influenced not only by the magnetic field but also by the electrostatic charge of toner particles. This study confirmed it by using two-dimensional numerical analysis. Simulation of toner dynamics was carried out using the Finite Difference Method (FDM) for the electric field calculation and the Distinct Element Method (DEM) for the calculation of charged magnetic toner motion in the magnetic and electrostatic field. The following were deduced form the investigation. (1) The chain length of toner particles was shortened by the toner charge. (2) In the case that particles does not include wrong-sign toner, charge distribution does not change the chain formation but wrong-sign toner particles influence the chain length and number. (3) The magnetic chain was reconstructed under the application of AC biased potential at the development gap. (4) Toner particles with wrong-sign toner caused a defect of chain images.