Abstract: Single AlF3 layers were deposited upon fused-silica substrates placed on a simulated fixture which has the same radius of curvature with the spherical element to characterize the optical and microstructural properties of the AlF3 films. First, transmittance and reflectance spectra of AlF3 layers at different positions on the fixture were measured by an UV-visible spectrophotometer from 185 nm to 800 nm, and their refractive indexes and extinction coefficients were obtained. Then the surface morphologies and surface roughnesses of AlF3 layers were assessed with an Atomic Force Microscopy(AFM). Finally, the X-ray Diffraction(XRD) was used to characterize the microstructure of AlF3 layers. Experimental results indicate that for AlF3 layers deposited at different diameters on the spherical element, their optical losses increase along with the diameters. The extinction coefficients of AlF3 layers at the edge position are 1.8 times of that at the center, and surface roughness are 17.7 times of that at the center. The results suggest that for the coating on the surface of spherical element, the difference in optical loss along the diameter caused by steam incident angles should be considered.