The invention discloses an ATE power supply test channel extension structure. The structure comprises a plurality of power supply test channels, each power supply test channel comprises a plurality of power supply extension branch circuits, each power supply extension branch circuit comprises a branch circuit selection switch and an overcurrent protection circuit, the overcurrent protection circuit is used for detecting the current of the corresponding power supply extension branch circuit, the connection of the power supply extension branch circuit and a detected device is maintained when the current of the current extension branch circuit is normal, the connection of the power supply extension branch circuit and the detected device is disconnected when the current extension branch circuit is overcurrent, and the condition that the overcurrent current extension branch circuit reduces the output voltage of the corresponding power supply test channel so that the tests of other power supply extension branch circuits of the same power supply test channel is influenced is avoided. The invention also discloses a test application method of the ATE power supply test channel extension structure. According to the ATE power supply test channel extension structure and the test application method thereof, the overcurrent isolation function is provided, and the test over-killing due to overcurrent during sharing of the power supply test channel by multiple branch circuits can be prevented.