Multi conjugate adaptive optics (MCAO) has been widely used in the large ground-base astronomy telescope, since it can enlarge the field-of view(FOV) and reduce the effect of atmospheric anisoplanatism. Only considering the anisoplanatism, with the assistance of the multi-thread adaptive optics simulator (MAOS), the difference of a conventional adaptive optics(CAO) and a MCAO system at the wavelength of 0.6 μm and 2 μm was studied respectively, it is quite obviously that in the visible band there is a significant improvement of the MCAO system than the conventional AO system. The influence of the second deformable mirror(DM) conjugate height was also discussed which had a key influence on the performance in the visible band, while the first one conjugated at the entrance pupil, and a preliminary study of the effect of DM order in the single adaptive optics system was provided in the end.