The invention relates to the technical field of composite material manufacturing and in particular relates to a method and a mold for manufacturing a flared carbon fiber pipeline. The mold comprises abase and an upper cover plate, wherein an open slot the shape of which is same as that of the bottom of a flared pipeline is provided with a carbon fiber composite material to form a lower profile laminate structure of the flared pipeline, and is higher than a platform of the base; bolted holes are formed in the platform and along the periphery of the open slot; the upper cover plate comprises acover edge, covers the open slot, is fixed on the platform by virtue of the cover edge and comprises an upper cover plate I, an upper cover plate II and an upper cover plate III; the carbon fiber composite material is laid on the upper cover plate I to form an outlet of the flared pipeline; the upper cover plate II is next to the upper cover plate I; and the carbon fiber composite material is laidon the upper cover plate III to form an inlet of the flared pipeline. The method provided by the invention can solve the problems of high ost and complicated process of conventional preparation methods, and the method and the mold can guarantee the reliable molding, convenient demolding and high yield of carbon fiber flared pipelines.