Film stress causes macro-bending deformation of the substrate,and the deformation makes incidence angles of beams vary at different points of the substrate.Based on the formula of spatial line included angle,the incidence angle at various points of the curve surface was computed.It is concluded that the same incidence beams have various incidence angles at various points of the curve surface and the incidence angle deviation is decided by the substrate curvature and the incidence location.Influences of the deviation on spectrum were analyzed,and experimental results show that the further away from reference point,the bigger the wavelength deviation is and are identical with the theory analysis.