Objective：To optimize the nailing path at trapezium of mineral external fixation for treating the fracture at the basilar of the first metacarpal，which can build more stable fixation and present safe and accurate operation. Methods：We measured the values of trapezium at multidimension by researching the computed tomography（CT） images of the bone at the multi-planer reconstruction （MPR） images，and analyzed them about the optimized nailing path design and feasibility. Results：The CT values of 60 people’s nor－mal trapezium were measured，including 30 men and 30 women with average age of 42.3. The radialis width of trapezium is （13.46±1.13） mm，middle altitude is （11.43±1.18） mm，altitude above shorten sagittal diameter is （7.38±0.98） mm，sagittal length is （14.59±1.63） mm. The measured values were used in locating nail tract. Conclusion：Most of the sizes of trapezium can meet the requirement of the optimization of nailing path；most of the measured values of trapezium can be used to evaluate the safe range of nail tract and provide guidance for the operation.