Off-axis paraboloid is commonly used in optical systems and collimator, its greatest advantage is that no central shelter. Difficulties of manufacture depend on the processing precision of mirror, focal length, aperture size and off-axis. As an asymmetry surface, it is really a hard work to manufacture a surface with an amount of large off-axis, large- diameter, large volume of non-sphere. Here, some of the techniques such as “the way of cutting from master mirrors”, “the way of filling up with sub mirrors”, “the way of polishing sub mirrors directly”, “the way of stretch deformations with stress” are discussed. Finally, some manufactures and results of master mirrors with diameter from 500 millimeters to 2000 millimeters are reported.