The invention relates to an alkali metal based aluminum nitride nano-material and a preparation method thereof. The technical scheme includes: firstly mixing 65-77wt% of sodium chloride, 2-6wt% of sodium fluoride, 8-12wt% of aluminum powder and 10-20wt% of sodium azide evenly to obtain a mixture, loading the mixture into a corundum crucible, then placing the corundum crucible in a tubular corundum furnace to carry out reaction at 850-1150DEG C in nitrogen atmosphere for 2.5-3.5h, performing cooling to room temperature, taking out the product, then washing the product 3-5 times, and conducting drying at 90-110DEG C for 4-8h, thus obtaining the alkali metal based aluminum nitride nano-material. According to the invention, the method is simple and the cost is low, the prepared alkali metal based aluminum nitride nano-material has high purity and excellent appearance characteristics.