Abstract: The photosensitive ZrO₂ sol was prepared from zirconium alkoxide and β-diketone by sol-gel method. The sol was dip coated on fused silex substrate. The films were exposed by high pressure mercury through a mask. The films were developed in ethanol to remove the unirradiated parts after irradiation. This process was repeated, then color separation gratings (CSG) were fabricated. The period of CSG is 210 μm, and the height of single step is about 500 nm. Nd：YAG laser was introduced to examine the diffractive index of CSG. The results of the experimental study of a CSG to separate the frequency tripling (355 nm) light from the basic (1 064 nm) and frequency-doubling (532 nm) light are presented. The intensity of designed diffraction orders amounted to about 88.4% for 355 nm, 5.7% for 1 064 nm, 4.2% for 532 nm, respectively.