Active support is a core technology of large ground-based telescope,which directly affect its observation capability,so it has attracted much attention all the time. The positioning system and support system of large ground-based telescope were summarized systematically. The positioning system contains three hard points and six hard points;The support system includes axial support with different types of actuators and radial support with different forms which contains “vertical push-pull support”、“slant push-pull” and “push-pull-shear”. The active support technologies of some foreign typical large telescopes are introduced and analyzed,which may provide a certain reference for active support design.