Abstract: Based on the polarization decomposition theory, the scattering field of the bar of the metal space frame is analyzed. The mechanical strength and scattering characteristics of the cylindrical bar and the rectangular bar are compared. Considering the advantages and disadvantages of the round bars and the rectangle bars, the optimal design of bars with rounded rectangular section is put forward. The radiation effect are simulated and analyzed. The results show that the rectangle bar has higher sidelobe level than the round bar due to the accumulation of electric charge on its edge, but performs better in resistance of bending. The rounded rectangle bar is a feasible scheme for improving both the mechanics and electromagnetics performance of the radome because of lower scattering intensity and higher mechanical strength.