Bone external fixation is an important treatment for limb orthopedics. There are some problems such as motion coupling and rotation dislocation in the existing fixator during limb rotation and stretching orthopedics. Drawing on the configuration advantages of RCM mechanism, a 2R1T centering orthopedic external fixation robot based on traditional Ilizarov external fixator is proposed in this paper. The proposed robot has centering motion characteristics and is easy to realize single freedom independent motion. Based on the Spinor theory, the mathematical analysis of the traditional fixation orthopedics is firstly carried out, then establish the Spinor system and anti-spinor system of the 2R1T centering fixation robot, and complete the branch chain selection and assembly. Finally, this paper analyzes the motion degree and workspace of the robot, and carries out the orthopedic dynamic simulation analysis and prototype experiment based on tibia motion trajectory. The experiment result shows that the rotation correction range of the robot is -15~ 15°, the error range is ±0. 5 °, the range of drafting correction was 0~ 30 mm, and the error range is ±0. 2 mm, which realizes the quantification and accurate regulation of orthosis and ensures the safety of limb orthopedics.