Abstract: By using the high frequency Infrared Absorption Spectrometric method, the determination of low levels of sulfur in ores was accurate; but not for the high sulfur content. High content sulfur in molybdenum ore and nickel ore was determined by CS-3000 High Frequency Combustion-Infrared Absorption Spectrometer in this study. The samples were burned at high-temperature and decomposed by adding the flux of the pure ion filings and tungsten grains. The measurement conditions such as sample amount, the quantity of flux and analysis time of the instrument have been optimized. The method was verified by national standard materials, the precision was less than 1% (RSD,n=9) and the sample recoveries ranged from 96.0% to 101.9%. Compared with the conventional barium sulfate gravimetric method, the accuracy of the method is less than 2% (relative error). The study focused on the matrix matching problem between samples and standard materials, and the influence of the matrix effect. The tests show that the content of sulfur between 1% and 35% in molybdenum ore and nickel ore can be determined accurately. The problem for the rapid and accurate determination of high content sulfur in molybdenum ore and nickel ore was solved.