The invention relates to a method for preparing a beryllium-copper alloy sheet, in particular to a method for preparing a high-quality beryllium-copper alloy sheet by adopting continuous multi-arc ion plating physical vapour deposition. The method for preparing the beryllium-copper alloy sheet by adopting the continuous multi-arc ion plating physical vapour deposition comprises the following steps: by using a pure Be metal target or a beryllium-copper alloy target with high beryllium content as a cathode, using a pure copper strip as an anode and adopting the multi-arc ion plating physical vapour deposition, depositing a pure Be or Be-rich film which is well combined on the single surface or on double surfaces of the pure copper strip; and then carrying out high temperature diffusion treatment to enable Be atoms to be diffused to permeate a pure copper matrix until the Be content in the copper strip reaches 1 to 3 weight percent, so that a Be alloy strip with excellent mechanical performance and electrical conductivity and Cu content of minus 1 to 3 weight percent is obtained. The method disclosed by the invention is simple and easy to operate, has high working efficiency, is energy-saving and environmental-friendly in the preparing process, has controllable quality and is very suitable for industrial application.