The invention relates to a material special for polyethylene and a preparation method thereof. The material special for the polyethylene has a uniform short branched chain structure, wherein melt index (MI21.6) is 1 to 3 grams per 10 minutes; average granularity is 200 to 300 mu m; bulk density is 0.35 to 0.40 g/cm<3>; and density is 0.947 to 0.950 g/cm<3>. Polyethylene powder for crosslinking to form a pipe is not required to be subsequently processed and crushed and can be directly distributed relatively reasonably; and in the crosslinking process, the same and even higher crosslinking degree is achieved under the condition of using a small amount of peroxide.