This work presents a new method of dynamic impedance matching for use in fixed-frequency resonant wireless power transfer (WPT) systems. In particular, a six channel Micro- Electromechanical System (MEMS) based switch is used to obtain variable shunt capacitance in a double-L matching network topology. A brief overview of the MEMS switch is provided and attention is then focused on its use in the context of resonant capacitive coupling WPT systems operating at 13.56 MHz and 27.12 MHz. Consideration of the MEMS switch voltage and current handling capabilities then leads to practical design limits. Measurements are carried out at a power level of 75 W and WPT impedance matching is demonstrated over a resonator displacement range of 100 mm – 200 mm. The performance of the proposed MEMS based double-L matching network is then compared against modelled results and analyzed in terms of matchable impedance range, impedance match accuracy, node voltages, and efficiency.