To investigate the effect of 27nt-miRNA on the differentiation of mesenchymal stem cells into vascular smooth muscle cells. The highly expression plasmids of 27nt-miRNA and anti-27nt-miRNA, and negative control plasmids were constructed, packaged with lentivirus and transfected into human umbilical cord mesenchymal stem cells (hUCMSCs). Collagen IV was added to induce hUCMSCs differentiation into blood vessel smooth muscle cells (VSMCs). The cell viability was measured by MTT assay. The expression of SMA, SM22α at mRNA and protein levels was determined by RT-PCR, immunocytochemical staining and Western blotting. Compared with the negative control group, the viability of the 27nt-miRNA overexpression group was decreased by 20.48% (P<0.05), and the expression of SMA mRNA and SM22α mRNA and protein was significantly increased (P<0.05); the viability of Anti-27nt-miRNA group was increased 18.07% (P<0.05), and the expression of SMA mRNA and SM22α mRNA and protein was decreased (P<0.05). In summary, 27nt-miRNA promotes mesenchymal stem cells differentiation into vascular smooth muscle cells and inhibits cells viability.