Disclosed is a protection cover allowing a handheld device to reversely discharge, which includes a bidirectional DC-DC converter and a charging/discharging controller arranged inside the protection cover so as to allow a first handheld device that is received in the protection cover to externally discharge electrical power thereof. The protection cover applies a removable external connection to electrically connect to a second handheld device so as to allow the first handheld device to reversely discharge, via the protection cover, to the second handheld device.