A circumferential seam type supersonic nozzle for metal gas atomization comprises a gas inlet pipe (4) connected with an external gas bottle. The gas inlet pipe is connected with an annular gas chamber (1) of the nozzle, the center of the nozzle is provided with a central hole (2), a supersonic gas spray pipe (3) of a circumferential seam structure is formed on the inner chamber wall and the outer chamber wall below the gas chamber and comprises stabilizing sections, contracting sections, throats and diffusion sections, a seam profile consists of symmetric curves, the profile of the whole spray pipe is the seam profile formed by the curves AB, BC and CD to take the axis of central hole (2) as the symmetry axis, the profile rotates by 360 degrees around the axis of the central hole (2) so that a curved surface is obtained, and an included angle alpha ranging from 0 degree to 6 degrees but not equal to 0 degree is formed by an extension line of a central line of each seam passage and the axis of the central hole of the nozzle in the profile of the gas spray pipe (3) passing through the axis of the central hole of the nozzle. The supersonic nozzle for gas atomization has the advantages that gas flow is uniform, turbulence level is low, and shock waves are absent in a flow field.