The invention discloses a preparation method of CrB or CrB2 powder, belonging to the technical field of ceramic powder preparation. The preparation method is characterized by uniformly mixing chromium oxide, amorphous boron powder and a certain amount of molten salt and then carrying out heat treatment on the mixture at 800-1100 DEG C for 0.5-2 hours under the protection of an inert gas, thus obtaining the CrB or CrB2 powder, wherein the mole ratio of chromium oxide to amorphous boron powder is 1:4 or 1:6; the byproducts generated after reaction, namely diboron trioxide and molten salt, can be removed by soaking the byproducts in hot water to dissolve the byproducts. The method has the technical effects that the method is low in synthesis temperature, short in synthesis cycle, simple in adopted production process and low in cost and is suitable for volume production; and the prepared CrB or CrB2 powder can be used for preparing structural ceramics, wear and high-temperature oxidation resistant coatings and the like.