The invention belongs to the technical field of bioengineering, and particularly relates to a genetic engineering strain capable of effectively secreting D-psicose 3-epimerase and a construction method thereof. A D-psicose 3-epimerase gene rdpe from rumen bacterium Ruminococcus sp. 5_1_39B_FAA is obtained firstly, recombinant plasmid pMA5-RDPE construction and bacillus subtilis conversion are conducted, and then constitutive and secretive expression of RDPE in bacillus subtilis is achieved. By comparing three glucose-induced promoters, the optimal inducible promoter P[xylA] is obtained, and the RDPE secretion level is increased remarkably. By knocking out the xylose utilization gene xylAB (xylA and xylB), the xylose metabolism pathway of bacillus subtilis is blocked, the secretion amount of RDPE is further increased, and the optimal induced concentration of the inducer xylose is reduced to 0.5% from 4.0%. Finally, the engineered strain 1A751SD-XR is evaluated in a 7.5 L fermentation tank, and the RDPE secretion level can be as high as 95 U / mL and 2.6 g / L.