The invention relates to a method for agglomerating ferromanganese alloy powder through microwave sintering and belongs to the field of new metallurgy technologies. The method includes the steps that firstly, ferromanganese alloy chippings are ball-milled, alloy powder with the grain being smaller than 200 meshes, alloy powder with the grain being larger than 200 meshes and smaller than 100 meshes and alloy powder with the grain being larger than 100 meshes are screened out and returned to be ball-milled; then the alloy powder with the grain being smaller than 200 meshes and the alloy power with the grain being larger than 200 meshes and smaller than 100 meshes are evenly mixed according to the mass ratio of 1 to 0-1 and are compacted, and a mixed material is obtained; the obtained mixed material are heated to the temperature of 1,100 DEG C to 1,200 through microwaves under the environment of introducing Ar2, the temperature is maintained for 5 min to 20 min, and a sintering product is obtained; and the sintering product is cooled to the room temperature in the air isolating environment, and after finishing is completed, and a block-shaped ferromanganese alloy is obtained; and residual ferromanganese alloy chippings are finished, and ball-milling process is carried out. By the adoption of the method for agglomerating the ferromanganese alloy powder through microwave sintering, the time spent on the ball-milling working procedure is saved, and energy consumed in the ball-milling working procedure is lowered, meanwhile the compressive strength of the sintering product is improved, and the volume density of the sintering product is improved.