A power supply boost control device and a fault location identification and judgment method for the power supply boost control device of this invention comprise a step of judging whether a power supply relay has a turn-on fault, a precharge circuit has a turn-on fault, or the power supply relay has a turn-on fault; second judgment unit is comprised for judging whether a boosting prohibit function is faulty, or the precharge circuit has a turn-off fault, or the precharge circuit has a turn-off fault; and third judgment unit is comprised for judging, based on the judgment result of the first voltage judgment unit, whether or not the power supply relay has a turn-off fault.