The invention relates to a method for implementing simplex communication based on a mobile phone terminal. Currently, when an interphone is in conversation, the voice thereof is unidirectional and few resources are occupied, however, the definition of the voice is relative poor, and signals can be easily interfered during conversation, so the conversation quality is poor. The invention provides the method for implementing the simplex communication based on the mobile phone terminal. The method is as follows: the mobile phone terminal dials a target number to start calling, and then a public network exchanger receives a calling signaling so as to forward a speech channel to an increment platform; after a called response is answered, a relay module builds speech channel butt and sends a butt time slot channel to an exchange module, and then the exchange module builds initial one-way voice exchange from calling to incoming call; a user presses a listen/speak key on the mobile phone terminal, a mobile phone software module simulates the key to transmit a dual-tone multifrequency (DTMF) key signal to the increment platform; a DTMF module monitors the key signal corresponding to the relay time slot in real time and analyzes whether the key signal is a simplex communication key signal; and after the key is matched, and the exchange module finds out the corresponding relay time slot and changes voice direction, the simplex communication between the mobile phone terminals is realized.