The invention discloses a composite-section simply supported beam and a manufacturing method thereof, which solve the problems of corrosion of internal reinforcing steel bars and influence on bearingcapacity of structure by the bending and cracking of the reinforced concrete simply supported beam in the prior art. The composite-section simply supported beam combines ECC (engineered cementitious composite) and common concrete, so as to improve the ductility of the member and overall durability. The composite-section simply supported beam adopts the technical scheme that the composite-section simply supported beam comprises a common concrete layer and an ECC layer, wherein the ECC layer is arranged at the outer side of the common concrete layer; the ECC layer and the common concrete layer are combined into a simply supported beam with a rectangular section by side crossing surfaces, and a debonding layer is arranged at the bottom crossing surface of the ECC layer and the common concretelayer; a reinforcement skeleton is arranged in the common concrete layer and is used as support.