Two heterotrophic nitrification aerobic denitrifying bacteria strains, WXZ-2 and WXZ-8, were immobilized by PVA-boric acid method. The optimal embedding conditions were obtained by orthogonal test method. The Quantity of entrapped bacteria was 4%. The concentration of PVA was 5%. The crosslinking time was 12 h. And the diameter of the immobilized beads was 2.5 mm. Two different drying methods, freeze-drying and drying at 40℃, were compared to keep the beads. It was proved that the beads dried at 40℃ showed much better activity, mechanical strength and adsorption performance.