The invention provides a marine microorganism Arthrobacter sp. YJ34 dextranase producing gene. An enzyme gene sequence is 1923 bp in total length, ATG is taken as an initial codon, TAG is taken as a terminal codon, and GC base content is 59.23 percent. The invention further discloses a dextranase gene recombinant engineering bacterim obtained through cloning of the dextranase gene and efficient expression in escherichia coli. The invention belongs to the technical field of enzymology and enzyme engineering. The recombinant engineering bacterium is built through gene cloning and sequencing, anda purified recombinant enzyme is obtained by induced expression and purification of a recombinant enzyme. The enzyme activity and enzyme stability are improved greatly. The optimal reaction temperature of the enzyme is 55 DEG C as determined according to the enzymatic property, and the optimal acting pH is 7.5.