Disclosed are an ultra-high molecular weight polyethylene resin for fiber and a preparation method thereof. The initial crystallinity of the resin is 60.5 to 90%, the volume average particle size is between 100 and 350 μm, the particle-size distribution is 1.0-2.1, the molecular weight is 2-7 million, the tensile breaking stress is 30 to 60 MPa, the bulk density of the resin is 0.10 to 0.50 g/cm3, the infiltration time in the solvent decalin is 0.5 to 11 min, the decalin absorption amount of the resin is 2 to 50 g of decalin per 100 g of ultra-high molecular weight polyethylene resin, and the white oil absorption amount is 5 to 60 g of decalin per 100 g of ultra-high molecular weight polyethylene resin. The ethylene homopolymerization is performed using a slurry polymerization process in the presence of a main catalyst and a co-catalyst.