The invention relates to a method for manufacturing a carbon fiber arm support for a concrete pump truck, which comprises the following steps of: arranging a hollow core mold, laying a raw material for manufacturing the carbon fiber arm on the external surface of the core mold, coating the exterior of the raw material by using a vacuum film, sealing both ends of the vacuum film on both ends of the core mold, arranging air exhaust holes on the vacuum film, putting the entire mold in an autoclave, pressurizing by using compression air, and curing to form by using an electric heating tube to heat. The carbon fiber arm support for a concrete pump truck, processed by using the method, fully exerts the advantages of high specific strength, large specific modulus, fatigue resistance and corrosion resistance of a carbon fiber reinforced epoxy resin composite material, so that the pump truck arm support has excellent performance, and the weight of the arm support can be reduced by 40-60%. Meanwhile, because no outer mold is used in the invention, the investment to molds, tooling and equipment is greatly reduced, and the product design can be changed conveniently. Meanwhile, the method can also be applied to the fields of fire truck arm supports, suspension arms of hoisting equipment, transmission poles, communication poles and the like.