The invention discloses a transformer substation inspection robot system for detecting equipment in a box and a method thereof. The transformer substation inspection robot system comprises a robot and an automatic unlocking system installed outside the box. The automatic unlocking system comprises an electromagnetic lock and a control device. The control device comprises a single-chip microcomputer, a wireless communication module, an electromagnetic relay, a door-closing limiting switch and an alarm module. The automatic unlocking system is installed on a box door. The control device is installed in a lock body. The electromagnetic lock can be remotely controlled to be opened or closed by the robot and can also be manually opened or closed through a key. Through communication with the automatic unlocking system, the box lock can be automatically opened, and therefore detection and operation of the equipment in the box can be realized; the automatic unlocking system is compatible with a common key unlocking mode, and therefore an automatic robot inspection mode and a traditional manual inspection mode can coexist; a robot pan-tilt is provided with a lifting mechanism, and therefore the range of the equipment capable of being detected by the robot is greatly expanded.