Mechanical loading device for closed test bench

The utility model discloses a mechanical loading device for a closed test bench. The mechanical loading device comprises a supporting seat assembly, a first loading moment disc shaft, a second loading moment disc shaft and a locking loading assembly, the supporting seat assembly is used for supporting the first loading moment disc shaft and the second loading moment disc shaft and comprises a bearing base, a bearing cover and a bearing; the first loading moment disc shaft comprises a first shaft and a second shaft; the second loading moment disc shaft comprises a third shaft and a fourth shaft; the fourth shaft is installed in the U-shaped annular groove of the second shaft, a plurality of concave grooves are formed in the circumference of the second shaft, fastening screw holes are formed in the concave grooves, and a fastening boss is arranged in the circumferential direction of the fourth shaft; the locking loading assembly comprises a plurality of connecting bolts and a plurality of fastening bolts, the c