Semitendinosus muscle composite flap was used to repair the neighbouring tissue defects. This is a admissible operation method. Accordingly, this article introduced our studies on semitendinosus muscle: 1. The length of the muscle renter was evaluated by regression equation. 2. Morphological characteristics the muscle, the source and distribution of the vessels were observed. The length of the pedicle of the vessel and external caliber were measured. 3. According to the clinic requrement, the muscle was divided at certain position and was turned upwards or downwards with the vascular pedicle to carry out the repair the defects of the gluteal, sacral, perineal or leg region, and so forth. This study provided the morphoiogical data of semitendinosus muscle composite flap for surgical application.