Abstract: In this paper， we report the preparation and performances of the solgel antireflective and protective coatings on KDP crystals. The AR coatings　with refractive index of 1.23 are of high transmission, the maximum of which　is large than 99%, and the laser d amage threshold is about 10J／cm2 for laser beam at 1.06μm and with pulse width of 1ns. The composition coatings methyl silicone and　porous silica reduced the threshold down to 5～8Ｊ/cm2.