To study the improving effect of regulatable gene of IL-3 engineered bone marrow stromal cell on the hematopoietic reconstitution in allogeneic bone marrow transplantation, an inducible gene expression system was established in a bone marrow stromal cell line which expressed IL-3 gene induced by doxycycline (Dox). The lethally irradiated mice C57BL/6 (H-2(d)) were co-transplanted with allogeneic bone marrow (BALB/c, H-2(d), 1 x 10(7)/mice) in which T cell were depleted by monoclonal antibody anti-Thy1.2 added with complement and the gene engineered stromal cell QXMSC1tet-on + IL-3 (5 x 10(5)/mice) at the same time. Dox was administrated continuously for 15 days to induce the expression of IL-3. The hematopoiesis in the bone marrow transplanted mice were observed at 30, 60 days post-transplantation, respectively. The numbers of RBC and WBC in peripheral blood were counted, and nucleated cells, CFU-S, CFU-GM, CFU-E and CFU-GEMM were measured in recipient bone marrow. The results showed that the engineered stromal cell line achieved high-level and controllable IL-3 expression. Co-graft with QXMSC1tet-on + IL-3 significantly increased the number of RBC, WBC in recipient peripheral blood, and the nucleated cells, CFU-S, CFU-GM, CFU-E, CFU-GEMM in bone marrow, compared with those coinfused with QXMSC1 or QXMSC1tet-on-TRE as control. In conclusion, regulatable gene IL-3 engineered bone marrow stromal cells accelerates hematopoietic reconstitution after allogeneic bone marrow transplantation.