The invention discloses a large-section underground excavation construction primary supporting tunnel-entering reinforcing structure for subway interval stop lines. The large-section underground excavation construction primary supporting tunnel-entering reinforcing structure comprises a section primary support arranged in a cross passage, a crossing primary support arranged on the bottom face of acrossing, an air passage temporary inverted arch arranged in the middle of the crossing, and a frame beam arranged on the outer contour within an interval main line horsehead range, and further comprises a single-tunnel double-line large section and a single-tunnel single-line standard section which are arranged in the frame beam; and the frame beam is of an n-shaped structure, and the frame beamis connected with the side wall of the cross passage. The n-shaped frame beam is additionally arranged on the outer contour within the horsehead range, stress systems at the interval main line horsehead can be transformed smoothly, loads are transferred onto the frame beam, and construction safety is ensured effectively.