The utility model discloses an unmanned aerial vehicle fuel cell's high -temperature early warning system, including installing the main fuel cell in the unmanned aerial vehicle organism and setting up in the reserve lithium cell of main fuel cell one side, main fuel cell installs a PCB board with the upper end of reserve lithium cell, the PCB board is proper down all to set up a power spliced pole to main fuel cell with reserve lithium cell, just the main fuel cell to the power spliced pole is provided with a metal contact -piece and the 2nd metal contact -piece with reserve lithium cell up end, be located an installation micro motor between main fuel cell and the reserve lithium cell, set up a driving lever on micro motor's the motor shaft, the one end of driving lever is the insulating segment, the other end is electrically conductive section. The utility model discloses an adopt a lithium cell backup battery's of a fuel cell mode, when main fuel cell temperature superelevation, automatic switch -over to backup battery prevents main fuel cell because the explosion or the leakage condition that the high temperature heat dissipation appears when not enough are used safelyr.