A 1X/2X reconfigurable rectifier with compact structure and consistent input capacitance under different modes is presented for wireless power transfer in implantable medical devices (IMD). Compared to the conventional design consisting of five switches and three comparators (5S3C), the proposed rectifier merely needs one switch and four comparators (1S4C) and greatly reduces the design complexity. It makes the input capacitance keep consistent during mode transition, and thus does not require extra input capacitance compensation circuit. Additionally, the proposed design eliminates the simultaneous conduction problem during mode transition. Simulation results in a commercial 0.18 um CMOS technology verified the proposed design.