Objective To establish a mouse's cross-territory ear flap that enables chronic, in-vivo observation of the change of vascular morphology. Methods 30 ICR mice, weighing 25～40 g, were used for this study. Commercial depilatory cream was used to first remove the hair of the mice, after which the vascular pattern in the ears was investigated. According to the observation of the vascular pattern in the mouse's ear, the eye scissors were used the sever the outer 2/3 of the base of the ear, in which process a ear's flap based on a vascular pedicle but crossed three vascular territories was created. After the creation of the flap, the mice were placed on an automatic controlled movable machine with the ear's flaps spread over a customized Plexiglas. Then the flaps were photographed under the stereoscope (×25) at the following time points: 1,2,3,5,7,10,14,21,30 d. the necrosis of the flap, and the morphological change of the vessels within the flap were analyzed. Results The ICR mouse's ear was supplied three angiosomes, which were respectively named as the cephalic, median and caudal angiosomes from inside out. Five days after the flap's creating, necrotic rate of(15±7)% was developed. The choke vessels between the medial and median angiosomes expanded rapidly in diameter, reaching the plateau 10d after flap creation, resulting the dilated choke veins and arteries at their peak being 3.9±0.5 and 3.5±0.7, respectively, than their initial sizes. The diameter of the choke veins began to shrink at approximately 10d, stabilizing after 21d. The diameter of the choke arteries plateaued and stabilized at around 10d. Conclusion ① after harvest of extended flap, the dilation of veins seemed to passive, whereas the dilation of arteries seemed to active; ② the number of the choke vessels between the dynamic and potential territories that are involved in dilation and extent of the dilation are much smaller than that of the choke vessels between the anatomic and dynamic territories;③ the mouse's ear flap is an excellent model of further study of mechanism underlining the dilation of choke vessels and for the screening of vasoactive drugs that augment the survival of the large flap.