The electrophotographic printing is the most suitable for color printing of the 50 ppm class, the authors decided to apply conventional technologies as much as possible. However, there were unique technological problems to solve for a color printer, such as the paper transport characteristic and transfer voltage because the tandem method is used for transferring toner images of four colors sequentially.Therefore, the authors studied the transfer process theoretically and experimentally to achieve ozone-free transfer at a low voltage with stable paper transport. According to the results of this study, a transfer roller was used for the high-speed transfer process using a dielectric belt and the voltage polarity of the dielectric belt was reversed. These measures achieved an ozone-free and low-voltage transfer. Stable paper transport conditions were also clarified to prevent a photoconductive drum from winding paper at the transfer process. In technological terms, it was proved theoretically and experimentally possible to transfer a negative charged toner with a negative transfer voltage under some voltage conditions of the dielectric belt. This added new information to printer process design.