The invention discloses a method and a device for removing iron ions and magnesium ions from a hot concentrated ammonium nitrate solution, and belongs to the technical field of ammonium nitrate. The device is provided with a settling tank, wherein the top of the settling tank is communicated with an ammonium nitrate solution feeding pipe; an ammonia atomizer is arranged in the settling tank and in a combining part of the round part and the conical part; a diluted ammonia feeding pipe is communicated with the ammonia atomizer; the settling tank is connected with an underground tank through a first pollution discharge pipe, a filter in front of a pump, and two paths of impurity removing pipelines of a second pollution discharge pipe; a discharging pipe of the settling tank is communicated with the top of a product tank through a conveying pump; a diluted acid atomizer is built in the bottom in the product tank; a diluted acid feeding pipe is communicated with the diluted acid atomizer. According to the method provided by the invention, 2 to 8 percent of diluted ammonia is added into the hot concentrated ammonium nitrate solution to form precipitates; then, 2 to 15 percent of diluted nitric acid is added for regulating the pH value of the solution. The iron ions and magnesium ions in the hot concentrated ammonium nitrate solution can be fast removed, and the decolored. The method is simple and can be easily understood; the effect is obvious; the hot concentrated ammonium nitrate solution with the clear and transparent color and high quality is provided.