In this study, two strains Halomonas and Aneurinibacillus were mixed in equal proportions as free cells that could degrade diesel and produce biosurfactant. A new type of immobilized cells, free cells immobilized in beads combined with sodium alginate and straw, was studied. The components of straw-alginate beads were optimized by Response Surface Method, and the degradation performance of immobilized cells was determined. The result indicated that the density, strength and broken rate of straw-alginate beads were 1.04 g/cm(3), 216 g and 4%, respectively. The best degradation rate of immobilized cells in straw-alginate beads could be 68.68%. Lately, by analyzing the Monod model, v(max) (maximum specific degradation rate of diesel) and K-S (half saturation rate constant) of immobilized cells in straw-alginate beads were 1.84 d(-1) and 3.23 g/L, respectively, which explained the higher degradation performance.