The invention provides a method for welding an ion-implanted surface-modified flame brazing aluminum-base composite material, which solves the problem that the aluminum-base composite material is difficult to braze by using a simple and practicable processing method and a welding process. The method comprises the following steps: carrying out surface modification on the aluminum-base composite material in an ion implantation device; clamping the aluminum-base composite material the surface of which is modified on a clamping apparatus, and scribbling brazing flux on the brazed joint; heating with frame so that the brazing flux is completely wetted and becomes spread, applying a uniform pressure, and melting the brazing flux so as to permeate into the brazed joint when the temperature of the aluminum-base composite material reaches about 390 DEG C, so that the aluminum-base composite material is completely wetted and becomes spread by the aid of the brazing flux; and cleaning the excessbrazing flux, keeping the temperature for some time, and naturally cooling. The welding process can effectively solve the application problem of brazing the aluminum-base composite material, and has practical value in the field of aerospace.