Isovist graph has been originally developed for 2D space analysis technology of urban and architectural space. This paper develops the isovist graph analysis technology from 2D to 3D for more clear evaluation of 3D environment and shows the simulation method of 3D isovist graph to analyze 3D environment more realistically than 2D. First, it is applied to a virtual 3D space model to show the difference between 2D and 3D simulation. Then it is applied to the real 3D space model of a university campus which includes height difference in its geography for validation of practical design use.