Optical thin films greatly constrain the performance improvement of optical systerm. The defects of optical thin films are highlight point both in theory and experiment. Choose TiO2,SiO2 as original materials and the typical defects of multilayer films which made by electron beam evaporation as research object. The morphology and composition were measured by scanning electron microscope (SEM). The result shows that the nodule defect is semisphere and composition correspond with the original material; defect formed by original material sputtering is pit and the content of Ti is much higher than nodule defect; one of the defects adhered on surface is irregular colloid contain with C which means this defect is organism; the other defects adhered on surface is block with arris and correspond with the original material.