The invention provides a magnesium metal reducing method which adopts a reducing mode using a vertical reduction pot, wherein the vertical reduction pot is arranged in a hearth, a vacuum pumping system is connected with the reduction pot, the reduction pot adopts an inner tube and outer tube structure, the inner tube is of a vertically movable structure, and the cross section of the containing part of the reduction pot is annular. According to the magnesium metal reducing method, when a material is charged, the inner tube is fixed in the outer tube; when the material is discharged, the inner tube is lifted, a sealing annular plate at the lower part of the outer tube is opened, and the reduced slag charge automatically falls; then the inner tube is fixed, the sealing cover at the lower part is covered for charging from the upper part, and proportioned pellets are charged in between the inner tube and the outer tube of the reduction pot; and the outer tube is heated for performing reducing reaction at the temperature of 1200+/-10 DEG C, the vacuum degree in the reaction vessel is 3-13Pa, and magnesium metal is obtained by condensing and collecting magnesium vapor at the upper part of the outer tube during reduction.