The invention relates to a large-diameter single-hole double-line subway tunnel and a construction method thereof. The large-diameter single-hole double-line subway tunnel comprises a tunnel body, a bottom plate, middle partition walls, a track bed plate, tracks, an evacuation platform, line pipelines and contact nets. The bottom plate is poured at the bottom of the tunnel body; the middle partition walls are vertically poured on the bottom plate; the track bed plate is horizontally arranged on the middle partition walls inside the tunnel body; the two tracks are arranged and laid on the trackbed plate; the evacuation platform is connected to the track bed plate and is located between the two tracks; the line pipelines are laid on the side wall of the tunnel body; the contact nets are installed on the top of the tunnel body and located over the tracks. According to the large-diameter single-hole double-line subway tunnel, uplink and downlink trains are arranged in the same tunnel to reduce the occupation of the underground space by about half, the construction is convenient, and costs are reduced.