At present, prepayment Watt- hour meter mainly uses IC,there are some shortages in the performance. The intelligent card used in this design is iButton,iButton is launched by Dallas Semiconductor (Dallas Semiconductor Corporation) . The design method of the prepayment Watt- hour meter by using iButton is introduced in this paper, characteristic and operation guide of iButton are emphasized. Method of hardware and software designing are discussed. Compared to IC system, this method has characteristics as easy op...