This paper presents a low-power MCU with remotely-programmable feature which is specifically optimized for implantable medical devices (IMDs). In medical applications the most critical requirements are low-power, energy-efficient, flexible, etc., which are provided by utilizing the techniques such as clock gating, power gating, instruction set improvement, DMA optimizations for data paths. The MCU has been verified correctly and fabricated with a scale of 79.1K equivalent gates, in standard 0.18μm CMOS technology.