The invention belongs to novel techniques of artificial crystal growth and in particular relates to a hexagonal laminar molybdenum diselenide powder material and a preparation method thereof. The preparation method of the hexagonal laminar molybdenum diselenide powder material comprises the following steps: by taking mono-molybdenum powder and mono-selenium powder as raw materials, putting absolute ethanol alcohol into the raw materials, mixing, performing primary ball milling, adding cosolvents, further adding absolute ethanol alcohol, and performing secondary ball milling, wherein the cosolvents comprise NaCl and KCl; drying a material after ball milling in a drying tank at 60-80 DEG C for 18-24 hours so as to form a material; grinding the material into fine powder, and pressing the finepowder into tablets; putting the tablets into a crucible, and putting the cosolvents NaCl and KCl into the crucible; calcining the crucible in the presence of nitrogen; cooling the calcined material,washing, and drying.