The disclosed interface device for SIM and USIM comprises: a bus interface module, a register module, an interruption-handling module, a clock generation module, a state machine module, a transmit-receive module, a card detection module, and a power supply module. Wherein, there are bus clock signal (pclk), bus chip-selection signal (p_cs), bus address line (paddr), and card power on-off control signal (sc_pwctrl). This invention expands SIM card from 2G times to the 3G times as USIM card, reduces cost and consumption, and prolongs mobilephone standby time.