The invention relates to a preparation method of spherical metal powder. The preparation method comprises the steps of heating a metal bar to melt in a heating device, so as to obtain melted liquid, and breaking the melted liquid into small droplets by using plasma as droplet breakage power, so that the small droplets are cooled and solidified and are collected so as to obtain the spherical metal powder. According to the spherical metal powder prepared by adopting the preparation method, almost no satellite particle exists, the oxygen content is less than 1200 ppm, and the occupancy of the powder below 53 mum reaches 90% according to weight percent; the spherical metal powder has the advantages of high degree of sphericity, narrow particle size distribution, low impurity content, good flowability, low oxygen content, no satellite particle, simple process, reliable technique, easiness in control over product particle size, high production efficiency and low inert gas consumption and is suitable for mass production, and the particle size distribution satisfies the 3D printing requirements.