The invention relates to a large-scale water tank internal leading screw distance measuring device. The large-scale water tank internal leading screw distance measuring device comprises a head end mounting board, a vernier caliper, a tail end mounting board, a measuring tool base and a block wherein the measuring tool base is a linear component, the head end mounting board and the tail end mounting board are respectively arranged on the measuring tool base, head and tail ends of the vernier caliper are respectively fixed on the head end mounting board and the tail end mounting board, a tail end of the measuring tool base is provided with the block, during measurement, a vernier of the vernier caliper and the block at the tail end of the measuring tool base respectively press against two to-be-measured leading screws. The large-scale water tank internal leading screw distance measuring device is advantaged in that a problem of incapability of measuring the leading screw center distancecaused by the over-large center distance of the leading screws and the too-close distance between the leading screw and the side wall of a water tank is effectively solved, and mounting quality of integral equipment is effectively guaranteed.