The invention discloses a preparing method of an Al-Ti-B refining agent for an aluminum wire. The Al-Ti-B refining agent is prepared through a two-step method. Firstly, under the high temperature, anAl-5Ti-1B intermediate alloy containing excessive Ti is prepared, an efficient TiB2 particle with a single TiAl3 layer on the surface is formed in Ti-rich melt in the intermediate alloy, the melt in the Al-5Ti-1B intermediate alloy is cooled, at the low temperature, Al-B intermediate alloy melt is added, excessive Ti is converted into TiB2, meanwhile, the efficient TiB2 particle with the single TiAl3 layer is reserved, and finally, the refining agent for the aluminum wire is prepared and contains the efficient TiB2 particle and does not contain excessive Ti. Through the refining agent, the aluminum wire has the good refining effect, and meanwhile, the excellent electrical conductivity is kept.