Foam structure in macro-scale has arisen recently as an impressive large span building structure which is the product of advanced structural design, radical architectural approach, and powerful computer-software technology. As a result of this interdisciplinary success, the efficiency of large span foam structure became an important question to answer which could lead further structural improvements. This study analyses efficiency of a large span foam structure relative to conventional large span building structures which are space frames by using a parametric simulation method. The analysis is based on the comparison of base cases of each structural types, which are developed on light of the real projects the Water Cube in Beijing,China and the Symbol Zone of Expo?70 in Osaka, Japan. The parameters of the analysis are structural depth, weight and displacement, and various vertical -horizontal load cases. The results were demonstrated with an aid of a structural simulation program. In conclusion, the results of this research has shown that foam structure is a preferable, new generation, steel building structure for large spans.