The invention discloses a manufacturing method of a large-sized branch pipe and a combined spherical shell branch pipe. The large-sized branch pipe is manufactured with a two-half combined structure, i.e., the large-sized branch pipe is manufactured into two half shells firstly, half main pipes and half branch pipes are manufactured on the two half shells respectively, and connecting flanges are manufactured on the combined edges of the two half shells. Before use, the two manufactured half shells are conveyed to a use place, the two half shells are combined together, the two half shells are connected into a complete large-sized branch pipe through bolts by using the connecting flanges, and the main pipe and the branch pipe of the large-sized branch pipe are formed by combining the half main pipes and the half branch pipes on the two half shells respectively. The combined spherical shell branch pipe is prefabricated and molded in plants, and has the advantages of easiness in manufacturing, material saving, low manufacturing cost, smooth inner surface, good hydraulic condition, high pressure bearing performance, convenience in transporting and high generality; and the two half shells are only required to be connected together by using bolts and nuts on field, and narrow field construction can be performed.