An audio adapter with a frequency modulation (FM) radio function is provided. The audio adapter includes an audio jack, an FM processing circuit, an audio codec, a digital interface, a memory and a processing unit. The FM processing circuit is configured to receive an FM signal through the audio jack and process the FM signal to generate an FM audio. The audio codec is configured to receive the FM audio and output an analog output audio containing the FM audio through the audio jack. The digital interface transmits power. The memory is configured to store multiple codes or program instructions. The processing unit is configured to execute the codes or program instructions to control the FM processing circuit to search for FM channel(s).