The invention relates to a method for preparing solid-dissolved high-bactericidal-activity nanometer Ag-Cu alloy powder by means of the in-liquid pulse energy technology. The method is characterized by sequentially comprising the steps that A, Ag and Cu are smelted together according to the proportion, wherein a solid-undissolved Ag-Cu target (5) is prepared according to the atomic percent of Ag larger than or equal to 40% and smaller than or equal to 90%, and a pulse laser (1), oxygen-free liquid (3), a container (4) and a support (6) are prepared; B, the target (5) is fixed to the support (6) and contained in the container (4), the oxygen-free liquid (3) is poured into the container (4), and the target (5) is completely immersed in the oxygen-free liquid (3); C, a laser beam (2) is generated by the pulse laser (1) to ablate the target (5), and powder-containing liquid is prepared; and D, under the inert atmosphere protection environment, the powder-containing liquid is separated, powder is extracted out, then the powder is dried, and the solid-dissolved high-bactericidal-activity nanometer Ag-Cu alloy powder can be prepared.