Nowadays, Japanese children in primary schools are using computers that aren't designed specifically for them, so their current environment isn't appropriate for their initial use of computers. The same is true for start up authentication systems. That is, since under the current system users have to input their names and passwords of alphanumeric characters from a keyboard to obtain certification, the system appears too difficult for Japanese primary school children who haven't yet learned the Roman alphabet. Therefore, in this study, a new password input interface was designed using icons with symbols familiar to primary school children, and then the system was evaluated by varying parameters such as numbers of icons and icon selection time and frequency. As a result, this study proposes a new password input interface suitable for primary school children.