The invention provides a metal ultrafine atomizing, crushing and grading system, comprising a metal smelting furnace, a metal hydrogen-discharging and heating furnace, a metal atomizing device, a fluidized bed depolymerization grader, a second precise grader, at least one collector, a filter and a compressor. The invention also provides a metal atomizing device, comprising a crucible, a spray disc, a spray cover and a cylindrical spray cylinder, wherein a circle of evenly distributed inclined holes is respectively arranged on at least two circumferences with different diameters of the spray disc; each inclined hole is provided with a Laval nozzle; and the extension line of each Laval nozzle is intersected with the central axis of the spray disc at the same point. Through the airflow with ultrasonic velocity, ultralow temperature and large velocity pressure generated by the nozzle in the metal atomizing device, the liquid metal or alloy is directly crushed, or rapidly cooled into atomized powder and then depolymerized by a fluidized bed and precisely graded by the precise grader to obtain metal fine powder and ultrafine powder with finer granularity, more even granularity and better granularity sphericity.