Objective To study the anatomic variation of bilateral anterolateral thigh（ALT）flap, serving as an anatomical basis for the necessity of preoperative selection of donor thigh. Methods Ten fresh cadavers（20 cases）were recruited for the fabrication of bilateral ALT flap. The nutrient perforating branches of each flap were found out and then traced reversely to the vascular pedicle. The type and the number of perforating branches were recorded,and the length and diameter of the perforator and vascular pedicle was measured. Statistic data was expressed as x±s. Results Three cadavers were found that the bilateral ALT flap were nourished by both septocutaneous and musculocutaneous perforators, while the other 7 cadavers were found not feeded by the exactly same perforator in types bilaterally. Only 3/10 of the cadavers were noticed sharing the same number of perforator bilaterally, while the remnant 70% not. All the septocutaneous perforators pass through the intermuscular septum between the vastus lateralis and rectus femoris muscle,and all the musculocutaneous perforators penetrate vertically or obliquely into the vastus lateralis. Perforators derived solely from descending branch of lateral femoris circumflex artery(LCFA) were observed in 14 cases. The other 6 cases, 2 of which from 1 cadaver bilaterally and 4 of which from 4 cadavers unilaterally, saw that both oblique branch and descending branch of LCFA gave off perforators into the flap. The length and diameter of each main perforator and vascular pedicle in 10 cadavers bilaterally were not different signific antly(P>0.05). Conclusion Nutritive perforating branch of bilateral ALT flap differed in type, number, course and pedicle sourse，which has direct effects on the difficulty of flap fabrication and the duration of operation. Preoperative selection of donor thigh is helpful for safe and rapid preparation of anterolateral thigh flap.