The invention relates to an asphalt concrete core wall first-stage and second-stage construction seam slot-shaped connection structure and a construction method and belongs to a rolling type asphalt concrete core wall dam construction seam structure and a construction method. A slot-shaped enlarged end head is adopted by a second-stage asphalt concrete core wall to wrap an end head of a first-stage asphalt concrete core wall; the joint of the first-stage asphalt concrete core wall and the second-stage asphalt concrete core wall is in the shape of a slope; and asphalt mortar is paved and poured in a connection seam slot of the side direction contact face of the first-stage asphalt concrete core wall and the second-stage asphalt concrete core wall. The asphalt concrete core wall first-stage and second-stage construction seam slot-shaped connection structure is novel in structure, high in deformation adaptability, good in anti-seismic performance, high in anti-seepage reliability, convenient to construct fast and favorable for energy conservation and environmental protection, well solves the problem that the technical limitation exists in a past asphalt concrete core wall stage construction seam structure and has good application prospects.