Objective:To investigate whether systematic implantation of bone marrow mesenchymal stem cells(BMMSCs)can promote the survival of expanded flap. Methods:BMMSCs of rats were isolated through the whole bone marrow adherent method and propagated to the third generation. When 90% cells were confluent,BMMSCs were digested and cultured. After three passages,cell immunophenotype of CD29+,CD90+,CD34- and CD45- were determined. A total of 20 Sprague-Dawley (SD)rats,weighing 300-350 g,were randomly divided into 2 groups equally:the control group and the treatment group. In the control group,a dorsal expanded skin flap across 3 areas was harvested and sutured back. In the treatment group,1 h after the harvest and suturing back of a dorsal expanded flap,1 ml of suspension of BMSC/100 g(1×106 cell/ml) was injected in the rats through the tail veins. One week later,the necrotic flaps of rats in both groups and the diameter of choke vessels between the iliolumbar angiosome and the intercostal angiosome were measured and compared. Results:Positive expressions of CD29,CD9,CD34 and CD45 were 99.3%,93.5%,0.82% and 2.22%,respectively,in the third generation of cell culture. One week after flap harvest,the necrotic rate of the flap was (29.4 ± 4.2)% in the control group,which was significantly larger than that in the treatment group[(10.4 ± 3.3)%,P < 0.001]. The diameter of choke vessels between the iliolumbar angiosome and the intercostal angiosome in the control group was(183 ± 25)μm,which was statistically smaller than that in the treatment group[(226 ± 23)μm,P = 0.001]. Conclusion:BMMSCs can obviously promote survival of expanded flap in rats through enhancing the dilation of choke vessels,and the mechanism of which remains to be further investigated.