The invention discloses an ATE (auto-test equipment) power test channel extension structure; an overcurrent protective circuit included in each power extension branch is used for detecting the magnitude of current of the corresponding power extension branch during test, and maintaining the connection between the power extension branch and a device under test when the current of a current extension branch is normal; the power extension branch and the device under test are disconnected when the current extension branch is under overcurrent, the current extension branch under overcurrent is prevented from pulling down output voltage of a corresponding power test channel and affecting the test of other power extension branches connected to the same power test channel. Each overcurrent protective circuit is also used for setting on-off state of the power extension branches during power-on startup. The invention also discloses a test application method of the ATE power test channel extension structure. The ATE power test channel extension structure has overcurrent isolation function, test overkill due to overcurrent when multiple branches share the power test channel can be prevented, and branch selector switches can also be saved.