Abstract: A POST (power on self test) debug system and method applicable to an electronic device is proposed. First, a reading module reads a POST code of a sub-routine to be executed when the electronic device is started up to execute a power on self test, and sends the POST code to a processing module. When the processing module receives the POST code, the processing module temporarily stores the POST code and detects whether the temporarily stored POST code has been changed at a predefined time interval. If no, the processing module records the temporarily stored POST code such that a user can fine reason for error according to the recorded POST code and repair the system timely. Such a debug system is simple and easy to implement.