Abstract: Along with the develop of Marine oil pollution treatment technology, the biological treatment technology have got much attention because it is a cost-effective, highly active and environmentally friendly method, among which the immobilization of strain can improve the degrading efficiency of oil degrading bacteria in bioremediation process.In the study, sodium alginate (SA) -calcium chloride were used to immobilize the oil degrading bacteria into microspheres, and the four-factor orthogonal test at three levels was carried out to optimize the parameters of the bacteria immobilization process which includes the concentration of sodium alginate, the bacterial suspension dosage, the concentration of calcium chloride and the cross-linking time).The result showed that the best immobilized condition was sodium alginate concentration 3%, bacterial suspension dosage 75%, calcium chloride concentration 3% and cross-linking time 30 h.Under these conditions, the 7 d absolute degradation rate of oil degrading bacteria microsphere was 48.7%, which was 28% higher than CK.