Abstract: Visual simulation is useful for designing, analyzing and testing a space-telescope on the ground. Based on the coordinate transformation theory and the equal-angle projection method, visible boundary of the telescope was deduced for different orientation, and the two-dimension visual simulation was carried out using a real star catalog and the world coast line data. Reasonable results show that when the space-telescope is pointing to the high latitude area, a distortion of the round visible boundary appears in the Equidistant Cylindrical Projection style map chart. And the visible area on the earth surface is expanded when the height of the space-carrier increases. The simulation was used to imitate the celestial background in a real testing of a space-telescope outdoor. It's useful in testing and providing space environment for space-telescope on the ground.