This paper presents an energy-efficient SoC dedicated for portable medical monitoring and intervention systems capable of closed-loop control. The SoC contains a 0.9V/165μW MCU and a dual-band RF block including a 403MHz transceiver for data link and a 915MHz receiver for wake-up link. The data link transceiver is composed of a 200kbps FSK transmitter and a 64kbps OOK receiver, consuming 5.58mW and 3.13mW, respectively. The 915MHz receiver based on wireless energy harvesting gives the SoC the unique power-silent work-on-demand capability, avoiding wasting energy during the idle-listening period. The power consumption of the integrated MCU is reduced by means of acceleration instructions and modules. The implemented work-on-demand MAC protocol with instant response satisfies the requirements of typical medical applications. The SoC is fabricated in 0.18um CMOS technology, and occupies a die area of 5.9mm2