The invention relates to the technical field of high speed railway double-block type ballastless track laying, in particular to an inner supporting type screw adjuster and a track skeleton positioning method. The inner supporting type screw adjuster comprises a crossbeam, tray adjusting devices, vertical adjusting rods and supporting rods; the tray adjusting devices are arranged at the two ends of the crossbeam and used for adjusting a track gauge; the two ends of the crossbeam are provided with vertical adjusting threaded holes located between the two tray adjusting devices; the peripheral surfaces of the vertical adjusting rods are provided with external threads matched with the vertical adjusting threaded holes so that the height of a track can be adjusted; the upper ends of the supporting rods are connected with the lower ends of the vertical adjusting rods, and the supporting rods are used for supporting the crossbeam. Due to the fact that the inner supporting type screw adjuster is located in a track skeleton, the situation that space outside the track skeleton is not enough and consequently the track skeleton cannot be supported at a preset position is avoided, the geometrical shape of the track cannot change, and the position of the track is free of offset.