Based on the coating design software,a type of λ/4-λ/2-λ/2 tri-layer broadband antireflective coating was deposited on the K9 substrate via sol-gel dip coating using tetrabutylorthotitanate and tetraethoxysilane as precursors. A broadband antireflective coating with a high average transmission of 99.25% (500-900 nm) was obtained, and the transmittance gain increased with the increasing incident angle. The main absorption peak of the Nd glass could be effectively covered even at an oblique incident angle range of 0°-60°, increasing the average transmittance gain from 7.2% to 10.2%. After heat treatment at 150 ℃, the film had a certain rubbing resistance and good surface uniformity with a root mean square roughness of 4.00 nm.