The invention discloses a water seal type emergency exhausting valve for a secondary combustion chamber. The water seal type emergency exhausting valve for the secondary combustion chamber comprises a valve door, a pressure valve cover, a maze type water seal structure, an ejector rod structure, a balancing rod, sealing water, an upper joint and a lower joint, wherein the upper joint and the lower joint are correspondingly arranged at the upper part and the lower part of the valve body and used for connecting the secondary combustion chamber and a smoke exhausting valve; the maze type water seal structure is arranged at the lower joint, and the sealing water is stored in the maze type water seal structure; the pressure valve cover is inserted into the sealing water in the maze type water seal structure in a reverse buckling manner; the pressure valve cover can be driven to vertically move up and down through the balancing rod, the ejector rod structure and a cylinder. According to the water seal type emergency exhausting valve, when the secondary combustion chamber runs normally, the cylinder can jack the balancing rod to press the pressure valve cover to enter a closed state; when in emergency, an electric system is powered off or stopped, a gas channel is controlled in way that the cylinder is in normal pressure loss state, and the balancing rod for pressing the valve cover can be automatically released, so that the valve cover can be quickly opened, and as a result, good emergency responding effect is achieved.