The invention discloses an electric-arc additive and hot-extrusion composite manufacturing method for an aluminum alloy complex component which is of a thin-wall deep cavity structure. The method comprises the following steps: step I, dividing the aluminum alloy complex component into a transverse connecting part and two side parts which are distributed asymmetrically relative to the transverse connecting part according to structure characteristics of the aluminum alloy complex component, taking one side part and the transverse connecting part into an integer as a first base body, and taking the other side part as a second base body; step II, manufacturing the first base body through a hot-extrusion forming method; step III, manufacturing the second base body on the first base body throughan electric-arc additive forming method, and taking the transverse connecting part as a base in the forming process to perform electric-arc additive manufacturing; and step IV, performing thermal treatment on the component obtained by processing. The electric-arc additive and hot-extrusion composite manufacturing method realizes high-efficiency, high-performance and high-precision manufacturing of the aluminum alloy complex component, improves processing efficiency, and greatly improves product quality performance.