There is a problem of low data transmission rate and signal reflection due to load impedance mismatch in narrowband power line communication (PLC). Thus a broadband PLC impedance matching method based on an inverted L-type matched attenuator is proposed. First, a third-order Butterworth T-type broadband bandpass filter module is designed and implemented based on the frequency, impedance and circuit transformation methods of normalized low-pass filters. Then, the impedance matching between PLC coupler and power line is realized by using a pure resistance matching network with inverted L-shape structure and adjusting the variable resistance elements in the trunk matching network by determining the impedance values at different frequency points. Finally, from the proposed impedance matching method, a PLC coupling circuit with 1~30 MHz bandwidth is designed and fabricated. The results of ADS simulation and experimental verification show that the proposed impedance matching method has good matching effect and easy adjustment of circuit parameters over a wider frequency range. It provides a new theoretical and practical basis for the design of PLC impedance matching.