The invention belongs to the field of high-entropy alloys, and particularly relates to a crystalline beryllium-containing high-entropy alloy material and a preparation method thereof. According to thealloy material, a beryllium element is added, and thus a CoCrFeNiBe high-entropy alloy with high specific strength is developed; due to the fact that the size of a beryllium atom is small, the difference between the size of the beryllium atom and the size of other component atoms is large, and the size difference of an alloy atom is conveniently improved; in addition, the mixing enthalpies of theberyllium and the other four elements have a small minus value, the delta of the high-entropy alloy can be changed at a large extent, and the delta Hmix of the high-entropy alloy can be changed at asmall degree through the micro adjustment of the content of the beryllium element, so that the organizational structure of the high-entropy alloy is obviously changed, the alloy is prevented from falling in an amorphous alloy region or an intermetallic compound region, and the solid solution phase high-entropy alloy is obtained; and moreover, the beryllium has the performance of being light in weight and high in specific strength, so that the hardness and the lightness of the series of high-entropy alloys are greatly enhanced, the density is reduced, and the specific strength degree of the alloy is increased.