The invention relates to a method for preparing high-strength high-damping MnCu-base alloy, belonging to the technical field of alloy preparation. The method comprises the steps: keeping MnCu-base mother alloy warm for 0.5-1h at 1000-1180 DEG C under the gradient magnetic field of 600T2/m, then cooling to the room temperature, and thus obtaining semi-solid solidified alloy; hot-rolling the obtained semi-solid solidified alloy, and then conducting solid solution treatment after cold rolling; putting a sample obtained after solid solution treatment into a magnetic field of 0.01-20T, keeping warm for 0.5-16h at 350-550 DEG C, then cooling to the room temperature, and thus obtaining the target MnCu-base alloy. Compared with the alloy with the same Mn content prepared by the prior art, the MnCu-base alloy prepared by the method has the advantages that the tensile strength is improved by 10-20%, the damped internal friction value is increased by 5-15% under the condition that the extension rate is basically not reduced.