The utility model relates to a downhole tramcar automatic monitoring device that derails, including sensor, processor module and alarm, sensor and pathway vertical are tangent, and the signal of monitoring transmits to the processor module in the electric termination rack of installing on the body frame through the hookup cable, and as mine car wheel during to deorbit, processor module controls an alarm police dispatch and shows the signal, the alarm is installed in electric termination rack. The side -mounting of every wheel pair is one monitoring devices, the monitoring devices mounted position is on the body frame, and is tangent with pathway vertical, be in same parallel lines with the wheel pair on. The utility model relates to a rationally, simple structure, convenient to use. Can move the in -process at the mine car and carry out automatic monitoring to the wheel pair circumstances in orbit.