A subrack comprising a chassis, a first main board region arranged in a front part of the chassis and a second main board region arranged at a rear of the chassis; characterized by the subrack further comprising: a first air duct arranged in the chassis, wherein the first air duct comprises a first air inlet and a first air outlet, the first air inlet is arranged on a front wall of the chassis and the first air outlet is arranged on a rear wall of the chassis, the first air inlet and the first main board region are oppositely arranged; and a second air duct arranged in the chassis and separated from the first air duct, wherein the second air duct comprises a second air inlet and a second air outlet, the second air inlet is arranged on the front wall of the chassis and the second air outlet is arranged on the rear wall of the chassis, the second air inlet is located below the first main board region; a first partition board, which is configured for separating the first air inlet from the second air inlet and is arranged between the first main board region and the second air inlet; a back board, which is arranged between the first main board region and the second main board region, wherein the back board comprises an opening communicated with the first air duct, and the second air duct is arranged below the back board; a first air exhaustion device, which is configured for driving air to be exhausted from the rear wall of the chassis and is arranged on the rear wall of the chassis, wherein the air enters the first air duct from the first air inlet, and then flows through the first main board region to the rear wall; and a second air exhaustion device which is configured for driving the air to be exhausted from the rear wall of the chassis and is arranged on the rear wall of the chassis and is separated from the first air exhaustion device, wherein the air enters the second air duct from the second air inlet, and flows through the second main board region to the rear wall; wherein the second main board region comprises a plurality of second sub-main boards arranged longitudinally; a diversion board is inclined and arranged between the second main board region and a lower wall of the chassis; and the diversion board is communicated with the plurality of second sub-main boards for guiding air in the second air duct into the plurality of second sub-main boards. a first air duct arranged in the chassis, wherein the first air duct comprises a first air inlet and a first air outlet, the first air inlet is arranged on a front wall of the chassis and the first air outlet is arranged on a rear wall of the chassis, the first air inlet and the first main board region are oppositely arranged; and a second air duct arranged in the chassis and separated from the first air duct, wherein the second air duct comprises a second air inlet and a second air outlet, the second air inlet is arranged on the front wall of the chassis and the second air outlet is arranged on the rear wall of the chassis, the second air inlet is located below the first main board region; a first partition board, which is configured for separating the first air inlet from the second air inlet and is arranged between the first main board region and the second air inlet; a back board, which is arranged between the first main board region and the second main board region, wherein the back board comprises an opening communicated with the first air duct, and the second air duct is arranged below the back board; a first air exhaustion device, which is configured for driving air to be exhausted from the rear wall of the chassis and is arranged on the rear wall of the chassis, wherein the air enters the first air duct from the first air inlet, and then flows through the first main board region to the rear wall; and a second air exhaustion device which is configured for driving the air to be exhausted from the rear wall of the chassis and is arranged on the rear wall of the chassis and is separated from the first air exhaustion device, wherein the air enters the second air duct from the second air inlet, and flows through the second main board region to the rear wall; wherein the second main board region comprises a plurality of second sub-main boards arranged longitudinally; a diversion board is inclined and arranged between the second main board region and a lower wall of the chassis; and the diversion board is communicated with the plurality of second sub-main boards for guiding air in the second air duct into the plurality of second sub-main boards.