Abstract: To reduce the risk of spontaneous combustion during coal storage and transportation, microbial desulfurization technology is used to reduce the content of inorganic sulfur in coal. A strain of Thiobacillus ferrooxidans was purified from coal mine water in Datong, Shanxi Province, and its desulfurization test conditions were optimized. Taking the removal rate of inorganic sulfur in coal as the response value, the main factors affecting the removal rate of inorganic sulfur were screened out by Plackett-Burman design method. Then, the steepest climbing test was carried out to obtain the test center point, the continuous variable surface model was established by response surface method, and the interaction of various influence factors was determined. The results show that the order of the three main factors influencing the removal rate of inorganic sulfur is temperature > coal particle size > desulfurization time, and the interaction between temperature and coal particle size has the greatest influence on the response value. The optimized desulfurization conditions are as follows: the temperature is 29.50 ℃, the coal particle size is 100 mesh, and the desulfurization time is 11.67 days. The removal rate of inorganic sulfur is 79.78%, which is close to the predicted value and the regression effect is good.