A system for automatically determining a temperature tolerance range of an electronic device directs a temperature regulator to regulate a temperature equaling a previous regulated temperature plus or less a temperature difference. When a determination module determines the electronic device has failed to power on or a test of the electronic device for testing hardware of the electronic device has failed after the electronic device is powered on at a regulated temperature, a limit value of a temperature tolerance range for the electronic device is ascertained. The limit value is equal to the regulated temperature, under which the electronic device has failed to power on or test has failed, less or plus the temperature difference.