The invention discloses a cast-in-place steel-concrete composite beam, which relates to a composite beam. The cast-in-place steel-concrete composite beam solves the problems that a reinforced concrete beam and a column connection node in the existing steel structure and the existing steel-concrete composite structure have complex structures and are difficult to construct, the problems that a common composite beam has a large steel consumption and a high structure manufacturing cost, and the problems that a composite beam of which the publication number is CN101215855 is complex in operation and is inconvenient to construct when connected with a reinforced concrete wall column, and has low bearing capacity, small rigidity, weak spanning capacity, large fracture width for tensile region concrete and small application range. Bottom flanges of two I-shaped steel beam sections of the cast-in-place steel-concrete composite beam and a tensile region steel plate are made into an integral body; a longitudinal steel plate ribbed stiffener is connected through a fire-resisting longitudinal bar; top flanges of the two I-shaped steel beam sections are connected through a tensile region longitudinal bar; stirrups are uniformly arranged along the longitudinal direction of the fire-resisting longitudinal bar; floor steel bars are paved on a stiffening framework of the composite beam; and concrete is poured on the floor steel bars and the stiffening framework of the composite beam. The cast-in-place steel-concrete composite beam is applied to civil engineering constructions.