The thick container load-bearing characteristics of heavy load-bearing frame, the optimization design based points symmetry principle and the optimization method based on the stress ribbon image in FEM were put forward, which have general guiding significance for the structure optimization of heavy load-bearing frame. According to the principles, the mechanical characteristics of the type ‘C’ and type ‘A’ frame were analyzed in detail and a series of valuable features of type ‘A’ frame was profoundly stated  which illustrated that it was scientific and correct for the 1200MN hydraulic press adopting type ‘A’ frame. Type ‘A’ frame is successfully designed and widely used. It is one of the most important contributions of Chinese engineering area to the world heavy manufacturing industry.