The invention provides a preparing method for ultrafine copper-aluminum alloy powder. The preparing method comprises the following steps that firstly, a metal solution in which the copper element and the aluminum element are mixed is subjected to high-speed atomization, rapid drying is conducted in the atmosphere with the temperature ranging from 180 DEG C to 230 DEG C through formed rotational flow, and ultrafine mixed metal chloride powder is generated; and secondly, after being collected, the product prepared in the first step is added in a reducing furnace, inflation of hydrogen is conducted for reducing and roasting, the product obtained after roasting is collected and screened, and the ultrafine copper-aluminum alloy powder is obtained. The preparing method has the beneficial effects that the product is similar single crystal particle alloy powder with the average grain size being 1 micron, and the alloy powder has the prominent beneficial effects of being good in fluidity, uniform in grain size distribution, high in compaction degree, large in specific surface area and the like.