The invention discloses a mined-out-area distributed optical fiber temperature monitoring and early warning system. The system comprises an underground industrial ring network, a ground monitoring computer arranged on the ground, a first optical transmitter and receiver, a second optical transmitter and receiver, a first mining temperature-sensing optical fiber and a second mining temperature-sensing optical fiber, wherein the first optical transmitter and receiver and the second optical transmitter and receiver are connected into the underground industrial ring network; and the first mining temperature-sensing optical fiber and the second mining temperature-sensing optical fiber are laid on a mined-out area. The ground monitoring computer is connected into the underground industrial ring network. The first mining temperature-sensing optical fiber and the second mining temperature-sensing optical fiber are laid in a square waveform shape in the mined-out area. And the first mining temperature-sensing optical fiber and the second mining temperature-sensing optical fiber are symmetrically laid and take a center line of the mined-out area as a symmetric axis. A first mining optical fiber temperature measurement host is arranged in a coal mine intake airflow roadway. A second mining optical fiber temperature measurement host is arranged in a coal mine air return way. The invention also discloses a mined-out-area distributed optical fiber temperature monitoring and early warning method. A temperature acquisition scope is wide, a signal transmission distance is long, monitoring precision is high and continuous temperature monitoring of the whole mined-out area can be realized.