Arginase from Bacillus cereus is successfully expressed in C. crenatum SDNN403 through shuttle plasmid pXMJ19 between Escherichia coli and Corynebacterium crenatum. Results of enzymatic determination show that an original bacterium has no activity of the arginase; enzyme activity of the arginase of a recombinant engineering bacterium is up to 24.3 U/mg. By using a whole-cell body of the recombinant engineering bacterium as a biocatalyst and the L-ornithine as a substrate, on the basis of enzymatic properties of the arginase, an optimal reaction temperature being 40 DEG C and pH being 9.0 are determined; 200ml of LBG cultivated recombinant bacterium is resuspended in 200ml of substrate buffer solution; the L-ornithine is produced by means of transformation under optimal transformation conditions; after 8h, 149.2g/L L-ornithine is acquired; molar conversion rate of substrate L-ornithine is up to 99.5%. The L-ornithine produced by the method has the advantages of high efficiency, high specificity, low energy consumption and the like.