Objective To investigate the mechanism of vascular stromal fraction (SVF) at the early stage after aspirated fat transplantation. Methods Fat was harvested from 5 cases of women undergoing abdominal liposuction operation, and SVF was isolated. Aspirated fat with (group B) or without (group A) SVF was injected subcutaneously into the back of nude mice, and the grafts were harvested at 1, 3, 5, and 7 days. Graft wet weight was measured; and immunohistochemical method (CD31) was performed and the secretion of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) were qnantified by Western blot assay. Results The wet weight of transplanted adipose tissue showed an increasing tendency in groups A and B with time, and no significant difference was found between groups A and B (P gt; 0.05). At 1 and 3 days after transplantation, no CD31 positive cells was seen in 2 groups; the CD31 positive cells of group B were significantly more than those of group A at 5 and 7 days (P lt; 0.05), and the CD31 positive cells at 7 days were significantly more than those at 5 days in 2 groups (P lt; 0.05). Western blot test showed that VEGF expression reached peak at 3 days , then decreased gradually; the expression of VEGF protein in group B was significantly higher than that in group A at 1, 3, and 5 days (P lt; 0.05). The expression of HGF protein in groups A and B remained at a high level within 5 days, but it tended to decrease at 7 days, which was significantly higher in group B than that in group A (P lt; 0.05). Conclusion SVF can enhance angiogenesis by secretion of growth factors at the early stage after aspirated fat transplantation.