A novel wireless intracranial pressure (ICP) monitoring system based on air pressure sensing is proposed in this work. Compared to the conventional implantable wireless ICP systems, the proposed system has the advantage of low damage to brain tissues and high measurement accuracy. A prototype device has been built with a commercial digital air pressure sensor and a dedicated SoC in 0.18μm CMOS which consists of the sensor interface, wireless transceiver and control logic. Experimental results show that the prototype implantable ICP device has achieved a resolution of 0.2 mmHg @ 9 samples per second, and a battery life of > 1 week.