Self-Detecting and Data Rewriting System and Application Method Thereof

A self-detecting and data rewriting system and application method thereof, mainly comprising: a computer with a data protecting unit installed internally that stores and records at least the computer's boot data and set hotkeys, and an external protection device that has an internal firmware collocated with a data storage unit, the external protection device includes an external connector to be connected with the computer to form information connection, so that the data storage unit is able to update automatically after comparing with and referring to the data protecting unit, to obtain the information of the booting and set hotkeys from the computer and stored and recorded in the external protection device. Thereby, when the computer fails to operate normally, use the external protection device to be connected to the computer so that the computer operating system can be restored and resumed with normal operation.