Abstract: A Digital Audio Broadcasting(DAB) system, which is based on advanced technique of Coded Orthogonal Frequency Division Multiplexing (COFDM), can provide improved per-formance of high robustness and virtual CD-like quality. In-Band On-Channel(IBOC) digital audio systems have the capability of simultaneously transmitting both analog and digital signals (in hybrid mode)within the allocated channel mask, allowing full compatibility with existing analog receivers, and will accomplish smooth transition from analog broadcasting to all-digital mode DAB at low cost. The authors analyze the spectrum of Frequency Modulation (FM) IBOC DAB, and presents basic structures of FM IBOC DAB transmitting system and receiver, introducing key technologies of Perceptual Audio Codcr(PAC), Forward Error Coding(FEC), OFDM, First-Adjacent Canceling(FAC), Time Diversity Delay (TDD)and Audio Blend(AB). By careful comparison and analysis, some advice on development of Chinese IBOC DAB is given.