Structural size optimization of a device for external bone fixation within a formed iterative hybrid optimization algorithm is presented in this paper. The optimization algorithm is in interaction with algorithms for generative design and FEM analysis and all integrated within CATIA CAD/CAM/CAE system. The initial model, representing the current design of the bone external fixation device Sarafix, was previously verified by experimental testing. The formed hybrid optimization algorithm is created as an integration of the global (SA method) and local (CG method) algorithm. The constraints of the optimization model are the clinical limitations of the interfragmentary displacements and the material strength. The optimized design has less weight, greater rigidity and less transverse interfragmentary displacements at the point of fracture compared to the current design.