A test system for adjusting a wireless communication device by impedance loading features includes a power supply for generating a plurality of voltages, a test fixture coupled to the power supply for generating impedances corresponding to a plurality of impedance loading areas, a test equipment coupled to a test point of the wireless communication device via the test fixture for measuring a plurality of radio frequency characteristic sets of the wireless communication device, and a decision device coupled to the test equipment for determining an optimal impedance loading area of the wireless communication device according to the plurality of radio-frequency characteristic sets.