Prefabricated PC stair mounting structure

The utility model discloses a prefabricated PC stair installation structure which comprises a floor slab and a PC stair, a positioning steel screw rod is embedded in the floor slab, a positioning hole is formed in the PC stair, a built-in cavity is formed in the upper end of the positioning hole, a limiting step face is arranged in the built-in cavity, a limiting gasket is installed on the limiting step face in an abutting mode, and a nut for locking the limiting gasket is installed at the upper end of the positioning steel screw rod. A built-in cavity is filled with cement paste, a gap between the PC stairway and the floor slab is filled with polyphenyl, the upper end of the polyphenyl is filled with a PE rod, the upper end of the PE rod is filled with sealant, a reinforcing supporting frame is installed between the lower end of the PC stairway and the side portion of the floor slab, bolt holes are formed in the lower end of the PC stairway and the side portion of the floor slab, the reinforcing supporting f