Myocutaneous flaps are excellent flap for head and neck reconstruction, but they have many problems on their survival length. Ideal myocutaneous flap sholud have an extensive thin, pliable skin segment, a small or moderate sized muscle block and a lengthy vascular pedicle. The survival quantity of random skin extensions has not been proved clearly. Ten porcine myocutaneous island flaps with random skin extensions were created and the survival length of random skin flaps were observed for 7 days. The boundary of survival flap was cleared on 7th day postoperatively. The survival length was largely influenced by surgical technique and the site of the flap. The survival length of random skin flap was maximally about 5.9-8.0 cm in each flap. That is, the myocutaneous flaps in our study sustained random skin flaps about 1.6 times their width of muscle block.