The invention aims at providing a dual-purpose, reliable and efficient low-backpressure welding exhaust hood of an industrial steam turbine. The low-backpressure welding exhaust hood can exhaust steam and enable the exhausted steam to enter a steam pipe net and can also exhaust steam and enable the exhausted steam to enter a condenser so that reliable and efficient running of a low-backpressure unit can be ensured. The welding exhaust hood comprises an upper exhaust hood half part and a lower exhaust hood half part. Each of the upper exhaust hood half part and the lower exhaust hood half part is formed by welding plates, pipes and blocks. The low-backpressure welding exhaust hood is high in strength and rigidity, good in manufacturability, simple in structure, low in pressure loss and high in efficiency. According to the low-backpressure welding exhaust hood, the requirements of different exhausting manners can be met on a larger range, and the beneficial effect of the simple structure of a backpressure type exhaust hood is inherited.