Combi card is a single chip smart integrated circuit card with dual interfaces including contact pads and contactless antenna. Using combi card make it possible to integrate the applications of banking by contact interface and transportation by contactless interface, so that various services can be provided with single card for multi-purpose. In this paper, the combi card's chip operation system that we designed is introduced. The contents include the communication protocol between card and reader and the commands provided by the card. File management and security control mechanism are also included. Finally, the method for ensuring the integrity of the data transacted by contactless interface is described.