The invention discloses a boiler pressure vessel exhaust duct. The boiler pressure vessel exhaust duct comprises a main exhaust pipe and a first electromagnetic valve. The first electromagnetic valve is fixedly arranged at the top of the main exhaust pipe. A pressure sensor is fixedly arranged at one side of the main exhaust pipe, and a pressure reduction pipe is fixedly arranged at the other side of the main exhaust pipe. A pressure reducer is fixedly arranged at one end of the pressure reduction pipe. An auxiliary exhaust pipe is fixed at one end of the pressure reducer. The main exhaust pipe and the auxiliary exhaust pipe are both composed of high temperature resistance layers, rubber layers and thermal insulating layers. The boiler pressure vessel exhaust duct is reasonable in design, low in cost and high in practicability. By the adoption of the pressure sensor, the pressure reducer is used for exhausting air through the auxiliary exhaust pipe, the pressure inside a boiler pressure vessel can be effectively reduced, and explosion caused by excessive pressure is prevented; due to the high temperature resistance layers, the rubber layers and the thermal insulating layers, pressure buffer capacity and anti-pressure capacity can be achieved, and the phenomenon of bursting explosion caused by excessive pressure is prevented; and meanwhile the phenomenon that the temperature of the main exhaust pipe and the temperature of the auxiliary exhaust pipe are excessively high and thus human bodies can be scalded can be effectively prevented.