The invention relates to a method for preparing polymer grade ethylene through hydrogenation. Raw materials consist of 99.99% (phi) or above of ethylene and 5-100ppm of acetylene. Reaction conditions include that the temperature of an inlet of a heat insulation bed reactor is 30-50 DEG C, the reaction pressure is 1.5-2.5MPa, and the volume airspeed is 2000-10000h<-1>. The hydrogenation catalyst is a Fe selective hydrogenation catalyst, a carrier is a high temperature resistant inorganic oxide, based on 100% by mass of the catalyst, the catalyst contains 1-8% of Fe and 0-1% of X, wherein the X is selected from one or several of K, La and Ce, the preferable content of the X is 0.5-1.2%, the specific surface area of the catalyst is 10-200m<2>/g, and the pore volume is 0.2-0.63ml/g. The catalyst is mild in reaction activity, good in operating flexibility, low in loss rate of the ethylene and even zero in the loss of the ethylene, and lower in the generation quantity of acrylic acid oligomer than that using a noble metal catalyst.