The manufacturing of large-scale diffraction gratings is always one of great tasks, and how to obtain meter-sized is also a very difficult problem. The appearance of the chirped-pulse amplification (CPA) promotes the need of gratings. Because of technological and financial limit, an alternative to mosaic two or more gratings into an equivalent single grating is proposed. Theoretical research of tiled-gratings is described, and experimental studies which include alignment errors test, accurate adjustment and stability control are also introduced.