The invention provides methods for sending and receiving a digital audio signal in a digital audio broadcasting system. Service data are scrambled and subjected to low density parity check (LDPC) coding, constellation mapping and sub-carrier interleaving at a sending end; service description information is scrambled and subjected to convolutional coding, bit interleaving and constellation mapping; system information is subjected to convolutional coding, bit interleaving and constellation mapping; the information and discrete pilots are multiplexed together and mapped to a corresponding spectrum mode to form an orthogonal frequency division multiplexing (OFDM) frequency domain symbol; and conversion of a frequency domain and a time domain is performed, a logic layer frame structure is formed by connection, and a physical layer frame structure is mapped from the logic layer frame structure and framed for transmission. The invention has the advantages that according to the spectrum characteristics of the conventional frequency modulation (FM) frequency range, a flexible spectrum mode is designed, and the conventional analog FM broadcasting signal is not influenced. The invention is expandable in spectrum, flexible in system transmission parameter setting and applicable to single-frequency network and multi-frequency network modes.