Abstract A three dimensional calculation of a first transfer subsystem in electrophotography is carried out and toner scattering on a transfer belt is simulated. This simulation consists of an electric field calculation and a toner movement calculation, and toner scattering around the periphery of the dot is investigated. The simulation shows that the formation of toner scattering arises from the toner jumping across the transfer gap before the photoconductor contacts the belt. The effects of transfer parameters on toner scattering are investigated with the simulation. To prevent toner scattering, the position of the roller, adhesion force, transfer bias, toner charge, and resistivity of the belt should be optimized to create an appropriate electric field distribution, and so that the toner transfer occurs in a small gap or in a contact nip between the photoconductor and the belt.