In order to overcome the shortcoming of space-borne rigid antenna reflector made of carbon fiber reinforced plastic(CFRP)skins with aluminum honeycomb sandwich(SAHS)structure,a new type of full CFRP skin plus rib(SPR)structure ring-focused parabolic surface antenna reflector with the size of 2.5 m×1.9 m is designed. Under the condition that the original caliber,surface type,and interface remain unchanged,the main influence factors are designed and controlled. First,from the perspective of high stiffness,lightweight,and easy to form,a finite element simulation software is used to analyze and optimize the layout of the rib,the cross-sectional shape of the rib, the size of the rib,and the matching of the size and the coefficients of thermal expansion(CTEs)of the rib and the skin. Second,two structures are prepared by the autoclave molding process. Third,the weight and the surface precision root mean square(RMS)value are measured. The results show that the fundamental frequency of the SPR structure is 142.2 Hz,which is 3.5 Hz higher;the number of the new structural parts is reduced by 40％,and the forming process is greatly simplified. The total weight of the new structure is 11.9 kg,lighter 42.5％,indicating that the weight loss is obvious. The RMS value is 0.15 mm,which is slightly lower 0.01 mm but satisfies the accuracy requirement not greater than 0.3 mm. It is proved that the SPR structure reflector is a superior structure of the lightweight spaceborne antenna reflector.