Rhodococcus sp. FS-1 ,which can specially break the C[single bond]S bond of dibenzothiophene (DBT) and convert DBT into 2-hydrobenzophene by "4S" pathway, is used to decrease the sulfur content in diesel oil. This research focuses on the diesel oil desulfurization using resting cells of Rhodococcus sp. FS-1. The research result indicate that the desulfurization activity of the resting cells of Rhodococcus sp. FS-1 was strongly high. When the concentration of DBT was 0.5 - 1.0mmol/L and the ratio of oil/water was 1:5, the effect of desulfurization was highest. The desulfurization rate was over 85 % when desulfurizing the diesel oil twice. GC analysis proves that this process did not break the carbon-carbon backbone. The calorific value of diesel oil is reserved.