The present invention discloses a method for transmitting signal between a central channel processing Main Unit (MU) and one or more Remote Radio Units (RRUs) by using SDH/OTN in Centralized Base Transceiver Station system using remote radio head (RRH) technology. The method includes: dividing the communication interface between the MU and the RRUs into a user plane and a control plane, the user plane mainly for carrying I/Q sampling data concerning the user data, and the control plane mainly for carrying the data concerning control signaling; forming the I/Q sampling data concerning the user data carried by the user plane into an I/Q data frame via an I/Q data frame adaptation layer, then forming the I/Q data frame into a GFP frame via GFP and transmitting it on SDH/OTN; and carrying the control signaling of the control plane on UDP/IP and/or TCP/IP, and further carrying IP packet on PPP and forming it into a frame by HDLC, transmitting the HDLC frame including the control plane signaling on the SDH/OTN via the control character channel of the GFP frame. According to the present invention, the existing SDH/OTN transmission network is utilized directly, which further reduces the management and maintenance operation needed for signal transmission, as well as networking cost.