In information visualization of social networks, force directed layout algorithms, which enable the creation of node-link diagrams of huge-graphs, are the most popular, however, they are not quite suitable for structural analysis and visualization which often produce images where nodes clump together in the center of the screen, making it hard to discern structural features. This paper proposes a Subgroup Analysis Layout (SAL) algorithm to solve this problem, which plots out and analyses the subgroups in social networks through the analysis of roles and key attributes. Then, the results of subgroup analysis are used to improve the force directed layout algorithm in both 2D and 3D visualization. Results with the case of terrorist organization information show that SAL algorithm can be excellent in analyzing and displaying the structure of social network.