Defects in thin films are one of the most important factors influencing laser induced damage in the thin film components at ArF laser system. In order to analysis the defects of fluoride thin films in wavelength of deep ultraviolet (DUV), LaF3 and MgF2 single layers, LaF3/MgF2 half high reflection (HR) coatings and HR coatings are prepared by thermal evaporation on CaF2, the laser induced damage thresholds (LIDT) at the wavelength of 193 nm for the LaF3 single layer and HR coatings are measured. Nomarski microscope is used to observe the surface defects and damage morphology. It is found that the LaF3 single layer surface becomes more smooth after the preparation, while the MgF2 layer appears a few defects, and the defects increase as the layer number goes up. Based on micrograph of the thin films, lots of defects play a leading role in HR coating damage mechanism at this condition.