The invention provides a novel enclosed steel-concrete composite beam which comprises a C-shaped steel beam on the lower portion. The composite beam is formed by fixedly arranged profiled steel plates on an upper flange and in a beam rib of the C-shaped steel beam and pouring concrete on the whole face layer of the profiled steel plates. The novel enclosed steel-concrete composite beam is simple in structure, high in composite action, quick and convenient to construct, capable of realizing industrialized production, evident in economic benefit and capable of being applied to civil building floor structures and plays an active role in promoting housing industrialization.