Objective In term of the issue that external fixator for distal radius fractures was lack of phased functional exercise of the wrist, a method for optimizing the design of external fixator structures based on transient analysis was proposed, so as to provide theoretical references for the design of external fixator structure. Methods Three working modes, namely, fixation, traction and flexibility were determined. Transient dynamic analysis was carried out targeting at the traction and flexibility mode of external fixator, so as to judge its stress and displacement changes under traction and flexibility loads. The key dimensions of external fixator were selected by sensitivity analysis, so as to screen out the important dimensions, and mass and maximum displacement were selected as target variables. Orthogonal test method and fuzzy optimization method were used to establish the mathematical model to change the multi-objective problem into a single objective problem, and then genetic algorithm was used to optimize the solution. Results The design of external fixator met design requirements in both traction and flexibility modes, with a stronger rigidity. The dimensional optimization has result ed in a 5% reduction in mass and an 8% reduction in maximum deformation compared to the original model. Conclusions This study achieves the goal of lightweight design and lays the foundation for improved design and research of external fixator for distal radius fractures.