Sulfur dioxide is the main air pollutant. It is directly related to the formation of haze. Flue is gas desulfurization. The primary measure of protecting the environment and reducing haze. Phosphate ore pulp flue gas desulfurization is a new desulfurization method in which desulfurization agent is phosphate ore pulp. The concentration of sulfur in solid and solution (phosphate rock, desulfurization liquid of phosphate rock and desulfurization slag) of phosphate ore pulp flue gas desulfurization agent were determined with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). By choosing a more sensitive analytical line of sulfur, the effects of operating conditions of the ICP spectrometer on the analysis results were investigated, at the same time, the sample preparation methods and coexisting ions which impact on determination results of sulfur was also considered. Phosphate rock, desulfurization liquid of phosphate rock and desulfurization slag were treated in three different ways to make sure the sample dissolved completely. 181.973 nm spectral line was chose as analytical line to avoid spectral interference of coexisting element. The incident power of 1 300 W, with observation height of 12 mm, the nebulizer gas flow of 0.65 L·min-1 and the pump flow rate of 1.5 mL·min-1 were selected. Under the optimum analytical conditions of spectrometer, the method was used for the determination of sulfur in phosphate rock, desulfurization liquid of phosphate rock and desulfurization slag with the detection limit of 0.000 38%, recoveries between 89.5% and 104.5%, and relative standard deviation (RSD≤2.30%). By comparing the results of barium sulfate gravimetric method, the findings were basically consistent with the relative deviation ≤3.88%. In conclusion, the method is simple and efficient, with high precision and accuracy, which can be used for research and routine production in phosphate ore pulp flue gas desulfurization.