—Integrated circuit (IC) design for a wireless BCI system is put forward in this paper. The system is composed of an electrode, a stimulator, antennas, and an integrated circuit including a preamplifier, an analog to digital converter (ADC), a current mode digital to analog converter (DAC), a transceiver and a micro control unit (MCU). The system is closed loop, which can detect and record electroencephalogram (EEG) signals, send the signals to computer wirelessly, and generate stimulating signals according to analysis results from the computer. A 16-bit ADC is designed and some non-idealities parameters (e.g. kT/C noise, 1/f Noise and so on) are given. Sub-threshold circuit technology is used to realize ultra low-power MCU. Both of the ADC and the MUC are verified by simulation results. Next work will include the design of the preamplifier, IDAC, and a single chip design integrating all the circuits.