This paper deals with the removing of pyritic sulfur from coal by means of biotechnology, which includes bioleaching and microbial retreat and floatation. The coal samples used , whose total sulfur was 2.30%, were taken from the Third Hongyang Mine in Shenyang. Through the process of bioleaching which lasted for 20 days, the total sulfur was reduced to 1.2% and the removing rate of sulfur was 47.83%. The suspension of thiobacillus ferrooxidans (T.f for short) can affect the desulphurizing results notably in the process of microbial retreat and floatation. Under the reasonable condition, the removing rate of sulfur can be increased by 10% or so in the period of microbial pretreatment which lasted for only 3 to 10 minutes.