An effective control method with improved energy efficiency and extended working range based on 1X/2X reconfi-gurable rectifier is presented for wireless power transfer in im-plantable medical devices (IMDs). Compared to the conventional method that fixes the duty cycle of the reconfigurable rectifier to be around 50%, the proposed method optimizes the duty cycle for different coupling and loading conditions, so the system effi-ciency is significantly improved and the workable coupling and loading range is greatly extended. Simulation results in a com-mercial 0.18 μm CMOS technology validate the proposed method.