A powder metallurgy high-entropy alloy comprises, by atomic percentage, 5-35% of iron, 5-35% of cobalt, 5-35% of chromium, 5-35% of nickel, 5-35% of manganese and 0.1-5% of nitrogen. A preparation method of the powder metallurgy high-entropy alloy includes the steps that high-entropy alloy powder is prepared, the high-entropy alloy powder is matched, after being mixed uniformly, the high-entropy alloy powder is placed in a ball mill to be subjected to ball milling, the particle shape of the high-entropy alloy powder after being subjected to ball milling is in the shape of a sphere uniform in particle size or a similar sphere, and the particle size range is 20-30 microns; and the high-entropy alloy powder after being subjected to ball milling is placed in a high-strength graphite mold to besubjected to vacuum hot pressing sintering, and finally furnace cooling is performed. The high-entropy alloy uniform in structure and fine in grain is obtained in a powder metallurgy method, and therefore the performance of the alloy is improved.