Impedance matching plays an important role in radio frequency circuits. To achieve dynamic load modulation in back-off operation for power amplifier or address the variation of antenna impedance due to complicated environment, tunable matching networks are demanded. To optimally design the coverage area within the Smith Chart for common ladder networks, analytic calculating procedure and computer optimization method has been proposed. The calculating procedure can be applied to arbitrary ladder networks and the optimization algorithm can acquire the optimal network automatically with appropriate constraints.