A system for controlling backup air brake for a locomotive, comprising: a backup brake valve, an equalizing reservoir, a relay valve, a pneumatic shut-off valve, and a cut-out cock, wherein: an inlet port of the backup brake valve is in communication with a first end of the cut-out cock, an outlet port of the backup brake valve is in communication with an air port of the equalizing reservoir, the air port of the equalizing reservoir is further in communication with a pre-control port of the relay valve and the first end of the cut-out cock, and a second end of the cut-out cock is communication with a main pipe; a supply port of the relay valve is in communication with the main pipe, a delivery port of the relay valve is in communication with an inlet port of the pneumatic shut-off valve, an outlet port of the pneumatic shut-off valve is in communication with a train pipe, and a control port of the pneumatic shut-off valve is in communication with the first end of the cut-out cock; the first end of the cut-out cock is in communication with the second end of the cut-out cock in case of the cut-out cock being turned on, and the first end of the cut-out cock is in communication with outside air in case of the cut-out cock being turned off; and the inlet port of the pneumatic shut-off valve is in communication with the outlet port of the pneumatic shut-off valve in case of a pressure at the control port of the pneumatic shut-off valve rising to a preset pressure, and the inlet port of the pneumatic shut-off valve valve is cut out from the outlet port of the pneumatic shut-off valve in case of a pressure at the control port of the pneumatic shut-off valve not rising to a preset pressure, the system for controlling backup air brake for a locomotive characterised by further comprising: a pressure sensor in communication with the delivery port of the relay valve, wherein the pressure sensor is configured to detect a pressure at the delivery port of the relay valve, and the pressure sensor is signally connected to the backup brake valve, to enable the backup brake valve to correct a control value for a pressure in the equalizing reservoir. an inlet port of the backup brake valve is in communication with a first end of the cut-out cock, an outlet port of the backup brake valve is in communication with an air port of the equalizing reservoir, the air port of the equalizing reservoir is further in communication with a pre-control port of the relay valve and the first end of the cut-out cock, and a second end of the cut-out cock is communication with a main pipe; a supply port of the relay valve is in communication with the main pipe, a delivery port of the relay valve is in communication with an inlet port of the pneumatic shut-off valve, an outlet port of the pneumatic shut-off valve is in communication with a train pipe, and a control port of the pneumatic shut-off valve is in communication with the first end of the cut-out cock; the first end of the cut-out cock is in communication with the second end of the cut-out cock in case of the cut-out cock being turned on, and the first end of the cut-out cock is in communication with outside air in case of the cut-out cock being turned off; and the inlet port of the pneumatic shut-off valve is in communication with the outlet port of the pneumatic shut-off valve in case of a pressure at the control port of the pneumatic shut-off valve rising to a preset pressure, and the inlet port of the pneumatic shut-off valve valve is cut out from the outlet port of the pneumatic shut-off valve in case of a pressure at the control port of the pneumatic shut-off valve not rising to a preset pressure, the system for controlling backup air brake for a locomotive characterised by further comprising: a pressure sensor in communication with the delivery port of the relay valve, wherein the pressure sensor is configured to detect a pressure at the delivery port of the relay valve, and the pressure sensor is signally connected to the backup brake valve, to enable the backup brake valve to correct a control value for a pressure in the equalizing reservoir.