Objective To observe the change law of density of choke vessels between the dorsal perforators, exploring the evaluation parameters of the enlargement of choke vessels. Methods Microvascular anastomoses (i.e. choke vessels) were chosen, the targeted area being designed as the flap model in rats, which was located between the left and right iliac lumbar perforasomes; then gelatin-lead oxide angiography was performed,the grey values of choke vessels area (V-valley) and perforasomes (V-peak) were measured in Scion Image Beta 4.02 and the ratio of them was calculated in various time points. Results The grey value ratios of choke vessels and perforasomes in 1h, 1d, 2d, 3d, 4d, 6d, 10d, 16d postoperatively were (0.29±0.05), (0.67±0.10), (0.78±0.08), (0.85±0.06), (0.60±0.12), (0.56±0.10), (0.53±0.11) and (0.41±0.07) respectively. Conclusions The choke vessels between the dorsal cutaneous perforasomes enlarge in 1h, peak in 3d, decline in 4d, and decrease gradually afterward. Calculation of the grey value ratio of choke vessels between perforasomes in the angiographic images is an optimal way to reflect the relative density of microvessels.