This invention provides a method for TrFO and PHS executing said method including the following steps: 1, generating a UDI channel between cell phone terminals A and B based on current signaling flow of the PHS, 2, terminal A tells the coder kind list supported by it and its preferred coding mode to terminal B, 3, terminal B selects a coder based on its supported coder list, the received coder list supported by A, its preferred coding mode and the current radio environment, 4, terminal B tells A its selected coder and its supported coder list, 5, A and B carry out TrFO communication with a selected coder.