Method for determining cause of engine stoppage using monitoring of ignition power

The present invention relates to a method and a system for determining a cause of engine stoppage using ignition power monitoring, which can determine whether engine stoppage is caused by keying off or by an ignition power problem through ignition power monitoring. The method for determining a cause of engine stoppage using ignition power monitoring according to the present invention comprises: an ignition power keeping determination step (S130) of determining whether the engine of a vehicle is in a key-on state where power is continuously applied to keep the engine running while being in a state (S120) where the vehicle is started (S110) and the engine is running; a power-off recognition time comparison step (S170) of comparing time for an electronic control unit (ECU) to recognize ignition power-off with prescribed malfunction determination ignition power-off recognition time if the engine is stopped by ignition power-off; a key-off operation determination step (S181) of determining that the engine is stopped by a key-off operation if the time for the ECU to recognize ignition power-off is longer than the malfunction determination ignition power-off recognition time; and a power abnormality determination step (S191) of determining that the engine is stopped by ignition power abnormality if the time for the ECU to recognize ignition power-off is not longer than the malfunction determination ignition power-off recognition time.