The invention discloses a method and a device for transmitting time division multiplexing service through an IP exchange network. The method comprises bearing TDM signals by using an IP pack, packaging the TDM signals into an IP net charge in a TDMoIP frame format, and transmitting to a packet switching network; and receiving the TDMoIP frame from the packet switching network, and carrying out corresponding service after extracting the TDM signals from the TDMoIP frame. The device comprises a TDMoIP frame organizing module, a transmitting module, a forwarding table searching module, a MAC / GMAC device, a receiving module, and a TDMoIP frame decomposing module, and may also comprises a TDM small switching module, a multiplexing module and a demultiplexing module. The invention achieves TDM signal package by using the IP pack so as to achieve more convenient and fast network capacity expansion, and the time gap interleaving multiplexing technique can improve the length of net charges of the TDMoIP frame so as to reduce the cost of pack-front catchword, MAC head and IP head of the Ethernet accordingly and improve the utilization rate of the network bandwidth.