A fabric with high shielding performance and a preparation method thereof are provided. The method includes: (1) selecting a polyester textured yarn with a denier ranging from 15 D to 50 D and a polyester filament yarn with a denier ranging from 15 D to 50 D as the yarns; (2) using three guide bars for knitting in a warp knitting machine; yarn lapping movement the first guide bar and the second guide bar use the polyester textured yarn, the first guide bar and the second guide bar knit with a modified warp plain fabric structure, the third guide bar uses the polyester filament yarns, and the third guide bar knits with a chain-stitch fabric structure; (3) jet dyeing performing a direct dyeing treatment on greige by a jet dyeing machine; and (4) carrying out a Stenter setting on a setting machine.