The theoretical calculation models for the rotating flat and spherical fixture configurations have been established respectively and the thickness uniformity of 2.6 m substrates in large aperture coater of 3.6 m in diameter have been studied. In order to improve the thickness uniformity, two sources and three sources have been employed. The thickness nonuniformity was acquired via the optimization calculations using the theory models. The optimal geometric configurations were obtained for two sources with the two rotating fixture configurations respectively, and the corresponding minima of thickness nonuniformity were 7.62% and 5.58%, respectively. For three sources, in the same way, the corresponding minima of thickness nonuniformity were 5.79% and 3.48%, respectively. It is found that compared with two sources, three sources can improve the thickness distribution to a great extent. Moreover, the thickness distribution obtained with the rotating spherical fixture configuration performs well as a whole.