Objective To explore the safe zone of sustentaculum tali screw fixation in treatment of calcaneal fracture.   Methods Morphologies of sustentaculum tali in intact dry calcaneus of 589 Chinese adult were investigated and classified. The clinically significant data were observed and measured in sustentaculum tali and calcaneus.   Results Type B calcaneus (77.92%) was defined as the most common type, and type A calcaneus (21.73%) was the second most common type. There were two osseous marks in the medial surface of sustentaculum tali: the posterior tip of middle articular surface for talus and the front end of medial margin of groove for flexor hallucis longus. In the medial of sustentaculum tali, the each side length of quadrilateral was (8.07±1.33)(3.88-12.31)mm, (10.27±1.57)(5.62-15.91) mm, (14.99±2.33) (5.86-21.87) mm and (15.43±2.16) (9.82-22.70) mm, respectively. The length of the its diagonal line was (15.83±2.94)(3.83-26.59) mm. The length of middle articular surface for talus was (18.97±2.85)mm (9.90-25.41).   Conclusion The quadrilateral in the medial surface of sustentaculum tali is the safe zone for sustentaculum tali screw fixation in treatment of calcaneal fracture.