A two-layer broadband antireflective (AR) film by sol-gel dip-coating process on K9 substrate for high power lasers was investigated which consists of a layer of methyl silicone polymer overcoated with porous silica The performance of two-layer film was changed little by dip and spin coating.The experimental result showed, when the physical thicknesses of silicone film and SiO2 AR film were suited and seemly, the two-layer AR film can be developed with transmission greater than 98% at the waveband range from 400 to 900 nm, of which damage threshold was over 20 J/cm2( 1064 nm, 4 ns).