The invention relates to extra-coarse grain tungsten carbide powder with narrow particle size distribution and a preparation method thereof. In the tungsten carbide powder, a particle size of 80-90 weight percent of tungsten carbide powder is between 0.5D50 and 2D50, and D50 is a median diameter; the tungsten carbide powder of which the particle size is larger than 5D50 is less than 0.5 weight percent; the purity of the tungsten carbide powder is higher than or equal to 99.9 weight percent; the Fisher particle size of the tungsten carbide powder is more than or equal to 15mu m. X-ray diffraction phase analysis is performed after ball-milling and crushing treatment, and the tungsten carbide powder does not contain W2C or other mixed phases. The preparation method of the extra-coarse grain tungsten carbide powder with narrow particle size distribution comprises the following steps: performing high-temperature hydrogen reduction on tungsten oxide, crushing hard agglomerates of extra-coarse tungsten powder, carrying out size grading, carbon preparation, high-temperature carbonization, and crushing and screening the carbonized tungsten powder. An extra-coarse grain WC-Co hard alloy produced by the prepared tungsten carbide powder is uniform in organizational structure, an average grain size of a WC hard phase is coarse, and the comprehensive performance of the alloy is good.