Objective To observe the effect of the expanded human umbilical cord blood CD34+cells in ischemic limb of mice and analyse the relationship between the CD34+cells and angiogenesis. Methods Human umbilical cord blood was collected and CD34+cells were separated for expanding. Mice limbs ischemia models were established (n=15) and randomly divided into three groups:expanded CD34+cells group (n=5),fresh CD34+cells group (n=5),and control group(n=5). CD34+cells were detected by DiI dye tracing and antihuman nuclear antigen antibody(HNA) immunohistochemical staining. The improvement of blood reperfusion was evaluated by indicators including limb temperature,CD31 staining,and transforming growth factor-β1 (TGF-β1) mRNA expression. Results On days 14 (t=5.421,P=0.001;t=0.616,P=0.000) and 28(t=10.780,P=0.000; t=12.123,P=0.000),both expanded CD34+cells group and fresh CD34+cells group enjoyed better temperature improvement. Days 28 later,the vascular densities in the expanded CD34+cells group and the fresh CD34+cells group were 592.3±24.6 (t=26.386,P=0.000) and 530.7±25.5 (t=21.502,P=0.000),which were significantly higher than that in control group 219.7±19.9. The TGF-β1 mRNA expression in the expanded CD34+cells group and the fresh CD34+cells group were (0.578±0.050) copies (t=12.376,P=0.000) and (0.504±0.080) copies (t=7.098,P=0.000),both over control group [(0.224±0.040)copies]. Conclusions In vitro culture of cord blood CD34+cells can emigrate to ischemic zone and induce angiogenesis to alleviate ischemia. Thus,it may provide a treatment option for lower limb ischemia.