A complex sphere radial tree visualization technique is proposed for visualizing large scale unstructured images based on stereographic mapping. The requirement model of visual organization and interaction for hierarchical images is first studied. Next, a hierarchical organization pattern is proposed, and layout algorithm is introduced for the visualization technique based on modified radial tree method and stereographic mapping. It gives the application instance of this technique on large-scale medical images. Results show that this visualization method can illustrate image contents while preserving global context in a certain space and provides powerful and effective support for users' analysis.