Abstract: Most sulfate and sulfide ores are composed of low electrical magnetic materials. In the process of combustion, the sulfur in sulfate and sulfide ores cannot be released completely, because it is difficult to produce a large enough electromagnetic induction eddy current. Thus, the results are lower than real values when the sulfur in sulfate and sulfide ores is determined by High Frequency Infrared Carbon-Sulfur Spectrometer. In this study, the barite and pyrite samples are diluted with silicon dioxide to acquire different contents of sulfur. By optimizing the sample weight and flux types, determination of sulfur by High Frequency Infrared Carbon-Sulfur Spectrometer was developed. Results show that the sample weight is 0.07 g when the content of sulfur is higher than 2% whereas sample weight is 0.1 g when the sulfur content is below 2%. Furthermore, the sulfur in barite and pyrite can be released completely into the infrared absorption area when adding 0.4 g of tin grain, 0.4 g of iron grain, and 0.5 g of tungsten grain to the sample. The recovery of sulfur can reach 95.8%-104.2%(barite) and 95.3%-105.1%(pyrite), which is far higher than the recovery of 83.3%-91.1% and 91.5-97.5% for the conventional analysis of sulfur by Infrared Carbon-Sulfur Spectrometer. This method precision is less than 5% and can determine the accurate content of sulfur.