Gram-negative bacterium, Pseudomonas delafieldii R-8 (CGMCC 0570) is capable of desulfurizing dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to produce corresponding monohydroxydimethylbiphenyl. The immobilization of the resting cells of this strain in Ca-alginate gel effectively improved the stability of the cells and the desulfurization ability per amount of cells. 1 mmol/L of DBT and 4,6-DMDBT could be completely degraded in about 1 d. About 39 percent of the activity for 4,6-DMDBT was recovered after immobilization. The desulfurization activity was increased with the decrease of the diameter of the beads. The Ca-alginate immobilized cells could be used repeatedly for over 190 h with the addition of calcium ions to strengthen them. A thin layer of hydrophobic polyurea was coated on the surface of Ca-alginate gel using a simple method. The desulfurization activity was enhanced after the coating.