The invention relates to a waste heat boiler for a quenching and cooling process of a suspended magnetization roasting powder of mine powder. The waste heat boiler mainly comprises a preposed evaporator, a flapper I, a suspended bed evaporator, a cyclone separator, a flapper II, a fluidized bed heat exchanger, a fluidized wind device II, a steam pocket, an oxygen remover, a dosing device and a pollution discharging system. The cooling process of the powder is effectively controlled and a cooling process that the powder is free of loss of excitation is realized through a three-section cooling process: the preposed evaporator, the suspended bed evaporator and the fluidized bed heat exchanger on the suspended magnetization roasting powder of mine powder in a metallurgical process. Waste heat in the powder is effectively utilized, the production energy consumption and the production cost of an enterprise are reduced, and the boiler mainly satisfies the metallurgical beneficiation process requirements, and is energy-saving and consumption-reducing, and has considerable economical value and social benefit.