Optical alignment is a crucial step in the commitment of a telescope.In this paper,the usual alignment procedure and method of the large alt-azimuth ground-base telescopes are described.It also includes the project methods of getting the better image quality in the all field of view and the general rule of alignments.The methods applied to the optical element and optical system such as Cassegrain and R-C.The alignment procedure mainly include the coarse adjustment and the fine adjustment to optical error.