Objective: To compare the clinical effects of interlocking intramedullary nailing and external fixator in the treatment of tibia and fibula fractures. Methods: 120 cases of tibia and fibula fracture patients were randomly divided into internal fixation group (n=70) and external fixation group (n=50), and the patients were treated with interlocking intramedullary nail and external fixation respectively. The operation condition and the motor functions of limb of patients in 2 groups were compared. Results: The lower limb motor function score of patients in internal fixation group was obviously higher than patients in external fixation group (P˂0.01), while the fracture healing time was obviously shorter (P˂0.01). There was no significant difference about full load time, intraoperative bleeding and operation time between internal fixation group and external fixation group (P>0.05). Conclusions: Compared with external fixation, treating tibia and fibula fracture with interlocking intramedullary nailing is beneficial to improve the limb motor function and shorten the healing time, so it is worthy of clinical application.