The utility model relates to the technical field of spray guns and flue evaporation devices, in particular to a spray gun and a flue evaporation device suitable for desulfurization wastewater. The spray gun comprises a spray gun body, wherein a liquid inlet end and an air inlet end which are communicated with a cavity of the spray gun body are respectively arranged at the left part of the spray gun body, a steam outlet end is arranged at the bottom of the right end of the spray gun body, a big-end-up conical atomizing nozzle is fixedly connected to the steam outlet end of the spray gun body, and a sealing jacket is fixedly connected to the outer side of the spray gun body positioned at the right side of the air inlet end. The device is reasonable and compact in structure; convenient use, the device comprises a spray gun, a flue, a dust remover and a desulfurizing absorption tower, according to the spray gun, the problems of local sludge accumulation of a dust remover, easiness in scaling at a nozzle outlet and blockage caused by ash accumulation in a desulfurization wastewater flue evaporation system of an existing spray gun are greatly reduced, the spray gun has the characteristics of safety, reliability, good desulfurization effect and easiness in control of an evaporation process in a flue, the operation is convenient, the working efficiency is improved, and the production cost is reduced.