In this work, we studied film thickness error in an electron beam evaporator with revolving structure. Using the noncosine film-thickness distribution theory, we propose a method for analyzing the film thickness error, in which the film is formed on the dome structure, and characterize the thickness error distribution using a mathematical method. Analysis shows that the film thickness error is the function of the location of film deposition, which is related not only to the mechanical configuration between evaporation source and substrate but also to the thin-film manufacturing parameters. Results reveal that the film thickness error comes from the deviation of the electron beam evaporation source from the axis of the revolving dome. We prepared a three-layer thin film on a 2700-mm-diameter coating machine. The film thickness error was retrieved using the spectral method. The results are consistent with the theoretical results of thickness error distribution.