This paper presents the implementation results of implantable cardioverter defibrillator (ICD) which is a mixed signal biomedical SoC implanted in human body to deliver appropriate therapies for heart arrhythmia. SoC technology is the best suited for low power consumption and device miniaturization because the ICD operates inside human body with limited power resources. The designed chip consists of three main parts: front-end circuit, bio-signal digital processor (BSP) and modem. The front-end circuit has roles of amplification and digital conversion of analog electrogram (EGM) signal. The BSP detects peak of EGM based on real time QRS detection algorithm. The BSP also controls defibrillator and pacing module to deliver appropriate therapies when BSP detect heart arrhythmia based on diagnosis and treatment algorithm. The modem transmits the episode when BSP diagnoses an arrhythmia and also can be used as an alarm when ICD cannot handle emergency situation. The proposed SoC is designed with capability of operating in 1.5V supply voltage and fabricated in a 0.18 μm CMOS technology with area of 6.5 mm2 and verified in realtime operation.