The present invention provides a method and a device for determining timeslot configuration in TDM transmission. The method includes: receiving consecutively transmitted TDM frames, wherein at least one TDM frame among the consecutively transmitted TDM frames includes a characteristic word; and according to a case of a timeslot collection occupied by the characteristic word in the TDM frame, determining a timeslot collection configured in the TDM frame for HDLC frames, wherein the characteristic word is configured to match a physical layer rate when no peer-peer protocol, PPP, link setup request packets are transmitted. Embodiments of the present invention are able to realize automatic acquisition of timeslot configuration of TDM frames.