The invention discloses a damage detection device for a transformer oil storage cabinet. The damage detection device comprises a shell, an optical signal generator arranged in the shell, an optical signal receiver arranged in the shell, a control system, a light intensity detection module and a transposition device. The control system comprises a first current sampling module, a second current sampling module, a comparison module and a control module. The first current sampling module and the second current sampling module are connected to the comparison module. The comparison module is connected to the control module. The optical signal generator and the optical signal receiver are connected to the control module. The light intensity detection module comprises a sliding plate, a seleniumcell A, a selenium cell B and a rack. The device transforms a detection optical signal into a detection electric signal. Through comparison with a current value, the damage case of a capsule is acquired. The device is easy to use, has a fast detection rate, greatly shortens capsule detection time and improves working efficiency.